diff --git a/.github/workflows/ets-from-source.yml b/.github/workflows/ets-from-source.yml
index af80d7484..5cc91fe09 100644
--- a/.github/workflows/ets-from-source.yml
+++ b/.github/workflows/ets-from-source.yml
@@ -24,7 +24,11 @@ jobs:
       - name: Install Qt dependencies for Linux
         run: |
           sudo apt-get update
-          sudo apt-get install qt5-default
+          sudo apt-get install qtbase5-dev
+          sudo apt-get install qtchooser
+          sudo apt-get install qt5-qmake
+          sudo apt-get install qtbase5-dev-tools
+          sudo apt-get install libegl1
           sudo apt-get install libxkbcommon-x11-0
           sudo apt-get install libglu1-mesa-dev
           sudo apt-get install libxcb-icccm4
@@ -33,6 +37,7 @@ jobs:
           sudo apt-get install libxcb-randr0
           sudo apt-get install libxcb-render-util0
           sudo apt-get install libxcb-xinerama0
+          sudo apt-get install libxcb-shape0
         shell: bash
         if: runner.os == 'Linux'
       - name: Cache EDM packages
diff --git a/.github/workflows/test-with-edm-3.8.yml b/.github/workflows/test-with-edm-3.8.yml
new file mode 100644
index 000000000..19c5cfd61
--- /dev/null
+++ b/.github/workflows/test-with-edm-3.8.yml
@@ -0,0 +1,80 @@
+# This workflow targets stable released dependencies from EDM.
+# Note that some packages may not actually be installed from EDM but from
+# PyPI, see ci/edmtool.py implementations.
+
+name: Test with EDM on Python 3.8
+
+on: pull_request
+
+env:
+  INSTALL_EDM_VERSION: 3.5.0
+
+jobs:
+
+  # Test against EDM packages on Linux
+  test-edm-linux-38:
+    strategy:
+      matrix:
+        toolkit: ['null', 'pyside6']
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Qt dependencies for Linux
+        run: |
+          sudo apt-get update
+          sudo apt-get install libegl1
+          sudo apt-get install libxkbcommon-x11-0
+          sudo apt-get install libglu1-mesa-dev
+          sudo apt-get install libxcb-icccm4
+          sudo apt-get install libxcb-image0
+          sudo apt-get install libxcb-keysyms1
+          sudo apt-get install libxcb-randr0
+          sudo apt-get install libxcb-render-util0
+          sudo apt-get install libxcb-xinerama0
+          sudo apt-get install libxcb-shape0
+          # Needed to work around https://bugreports.qt.io/browse/PYSIDE-1547
+          sudo apt-get install libopengl0
+        if: matrix.toolkit != 'null'
+      - name: Cache EDM packages
+        uses: actions/cache@v2
+        with:
+          path: ~/.cache
+          key: ${{ runner.os }}-3.8-${{ matrix.toolkit }}-${{ hashFiles('ci/edmtool.py') }}
+      - name: Setup EDM
+        uses: enthought/setup-edm-action@v1
+        with:
+          edm-version: ${{ env.INSTALL_EDM_VERSION }}
+      - name: Install click to the default EDM environment
+        run: edm install -y wheel click coverage
+      - name: Install test environment
+        run: edm run -- python ci/edmtool.py install --runtime=3.8 --toolkit=${{ matrix.toolkit }}
+      - name: Flake8
+        run: edm run -- python ci/edmtool.py flake8 --runtime=3.8 --toolkit=${{ matrix.toolkit }}
+        if: matrix.toolkit == 'null'
+      - name: Run tests
+        run: xvfb-run --server-args="-screen 0 1024x768x24" edm run -- python ci/edmtool.py test --runtime=3.8 --toolkit=${{ matrix.toolkit }}
+
+  # Test against EDM packages on Windows and OSX
+  test-with-edm-38:
+    strategy:
+      matrix:
+        os: [macos-latest, windows-latest]
+        toolkit: ['null', 'pyside6']
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v2
+      - name: Cache EDM packages
+        uses: actions/cache@v2
+        with:
+          path: ~/.cache
+          key: ${{ runner.os }}-3.8-${{ matrix.toolkit }}-${{ hashFiles('ci/edmtool.py') }}
+      - name: Setup EDM
+        uses: enthought/setup-edm-action@v1
+        with:
+          edm-version: ${{ env.INSTALL_EDM_VERSION }}
+      - name: Install click to the default EDM environment
+        run: edm install -y wheel click coverage
+      - name: Install test environment
+        run: edm run -- python ci/edmtool.py install --runtime=3.8 --toolkit=${{ matrix.toolkit }}
+      - name: Run tests
+        run: edm run -- python ci/edmtool.py test --runtime=3.8 --toolkit=${{ matrix.toolkit }}
diff --git a/.github/workflows/test-with-edm.yml b/.github/workflows/test-with-edm.yml
index f3c7106ea..6ff7e9d98 100644
--- a/.github/workflows/test-with-edm.yml
+++ b/.github/workflows/test-with-edm.yml
@@ -22,7 +22,11 @@ jobs:
       - name: Install Qt dependencies for Linux
         run: |
           sudo apt-get update
-          sudo apt-get install qt5-default
+          sudo apt-get install qtbase5-dev
+          sudo apt-get install qtchooser
+          sudo apt-get install qt5-qmake
+          sudo apt-get install qtbase5-dev-tools
+          sudo apt-get install libegl1
           sudo apt-get install libxkbcommon-x11-0
           sudo apt-get install libglu1-mesa-dev
           sudo apt-get install libxcb-icccm4
@@ -31,6 +35,7 @@ jobs:
           sudo apt-get install libxcb-randr0
           sudo apt-get install libxcb-render-util0
           sudo apt-get install libxcb-xinerama0
+          sudo apt-get install libxcb-shape0
         if: matrix.toolkit != 'null'
       - name: Cache EDM packages
         uses: actions/cache@v2
diff --git a/chaco/axis.py b/chaco/axis.py
index d2818e168..9635b8fe5 100644
--- a/chaco/axis.py
+++ b/chaco/axis.py
@@ -10,6 +10,8 @@
 
 """ Defines the PlotAxis class, and associated validator and UI.
 """
+import logging
+
 # Major library import
 from numpy import (
     array,
@@ -58,6 +60,8 @@
 from .label import Label
 from .log_mapper import LogMapper
 
+logger = logging.getLogger(__name__)
+
 
 def DEFAULT_TICK_FORMATTER(val):
     return ("%f" % val).rstrip("0").rstrip(".")
@@ -500,20 +504,21 @@ def _compute_tick_positions(self, gc, overlay_component=None):
             screenlow, screenhigh = screenhigh, screenlow
 
         if (
-            (datalow == datahigh)
+            (datalow >= datahigh)
             or (screenlow == screenhigh)
             or (datalow in [inf, -inf])
             or (datahigh in [inf, -inf])
         ):
+            if datalow > datahigh:
+                logger.warning(
+                    "{self.mapper} has an invalid data range with "
+                    "low={datalow} > high={datahigh}; unable to compute axis "
+                    "ticks."
+                )
             self._reset_cache()
             self._cache_valid = True
             return
 
-        if datalow > datahigh:
-            raise RuntimeError(
-                "DataRange low is greater than high; unable to compute axis ticks."
-            )
-
         if not self.tick_generator:
             return
 
diff --git a/chaco/multi_array_data_source.py b/chaco/multi_array_data_source.py
index 1c2aa8347..9663bb90e 100644
--- a/chaco/multi_array_data_source.py
+++ b/chaco/multi_array_data_source.py
@@ -13,7 +13,7 @@
 import warnings
 
 # Major package imports
-from numpy import nanmax, nanmin, array, shape, ones, bool, newaxis, nan_to_num
+from numpy import nanmax, nanmin, array, shape, ones, newaxis, nan_to_num
 
 # Enthought library imports
 from traits.api import Any, Int, Tuple
diff --git a/chaco/plot_containers.py b/chaco/plot_containers.py
index 7ee0046e6..f5eaa4df4 100644
--- a/chaco/plot_containers.py
+++ b/chaco/plot_containers.py
@@ -18,6 +18,7 @@
     array,
     cumsum,
     hstack,
+    resize,
     sum,
     zeros,
     zeros_like,
@@ -182,7 +183,7 @@ class GridPlotContainer(BasePlotContainer):
 
     # The internal component grid, in row-major order.  This gets updated
     # when any of the following traits change: shape, components, grid_components
-    _grid = Array
+    _grid = Array()
 
     _cached_total_size = Any
     _h_size_prefs = Any
@@ -510,7 +511,7 @@ def _reflow_layout(self):
             numrows, numcols = divmod(len(self.components), self.shape[0])
             self.shape = (numrows, numcols)
         grid = array(self.components, dtype=object)
-        grid.resize(self.shape)
+        grid = resize(grid, self.shape)
         grid[grid == 0] = None
         self._grid = grid
         self._layout_needed = True
diff --git a/chaco/plots/image_plot.py b/chaco/plots/image_plot.py
index 30284542a..a76b8f44d 100644
--- a/chaco/plots/image_plot.py
+++ b/chaco/plots/image_plot.py
@@ -22,13 +22,12 @@
 from traits.api import (
     Bool,
     Enum,
+    Float,
     Instance,
-    List,
     Range,
     Tuple,
     Property,
     cached_property,
-    Union,
 )
 from kiva.agg import GraphicsContextArray
 
@@ -84,7 +83,7 @@ class ImagePlot(Base2DPlot):
 
     # Tuple-defined rectangle (x, y, dx, dy) in screen space in which the
     # **_cached_image** is to be drawn.
-    _cached_dest_rect = Union(Tuple, List, transient=True)
+    _cached_dest_rect = Tuple(Float, Float, Float, Float, transient=True)
 
     # Bool indicating whether the origin is top-left or bottom-right.
     # The name "principal diagonal" is borrowed from linear algebra.
@@ -285,7 +284,7 @@ def _compute_cached_image(self, data=None, mapper=None):
 
         # Update cached image and rectangle.
         self._cached_image = self._kiva_array_from_numpy_array(data)
-        self._cached_dest_rect = screen_rect
+        self._cached_dest_rect = tuple(screen_rect)
         self._image_cache_valid = True
 
     def _kiva_array_from_numpy_array(self, data):
diff --git a/chaco/plots/tests/test_image_plot.py b/chaco/plots/tests/test_image_plot.py
index 448af7637..afed30367 100644
--- a/chaco/plots/tests/test_image_plot.py
+++ b/chaco/plots/tests/test_image_plot.py
@@ -37,7 +37,7 @@
 # The Quartz backend rescales pixel values, so use a higher threshold.
 MAX_RMS_ERROR = 16 if ETSConfig.kiva_backend == "quartz" else 1
 
-IMAGE = np.random.random_integers(0, 255, size=(100, 200)).astype(np.uint8)
+IMAGE = np.random.randint(0, 256, size=(100, 200)).astype(np.uint8)
 RGB = np.dstack([IMAGE] * 3)
 # Rendering adds rows and columns for some reason.
 TRIM_RENDERED = (slice(1, -1), slice(1, -1), 0)
diff --git a/chaco/ticks.py b/chaco/ticks.py
index 9eb160f81..284cb742b 100644
--- a/chaco/ticks.py
+++ b/chaco/ticks.py
@@ -305,6 +305,8 @@ def auto_ticks(
 
     if upper > end:
         end += tick_interval
+    if isnan([start, end]).any():
+        return []
     ticks = arange(start, end + (tick_interval / 2.0), tick_interval)
 
     if len(ticks) < 2:
diff --git a/chaco/tools/lasso_selection.py b/chaco/tools/lasso_selection.py
index cc17851f8..fa446189d 100644
--- a/chaco/tools/lasso_selection.py
+++ b/chaco/tools/lasso_selection.py
@@ -158,11 +158,11 @@ def normal_mouse_down(self, event):
         """
         # We may want to generalize this for the n-dimensional case...
 
-        self._active_selection = empty((0, 2), dtype=numpy.bool)
+        self._active_selection = empty((0, 2), dtype=bool)
 
         if self.selection_datasource is not None:
             self.selection_datasource.metadata[self.metadata_name] = zeros(
-                len(self.selection_datasource.get_data()), dtype=numpy.bool
+                len(self.selection_datasource.get_data()), dtype=bool
             )
         self.selection_mode = "include"
         self.event_state = "selecting"
@@ -197,7 +197,7 @@ def selecting_mouse_up(self, event):
         self._update_selection()
 
         self._previous_selections.append(self._active_selection)
-        self._active_selection = empty((0, 2), dtype=numpy.bool)
+        self._active_selection = empty((0, 2), dtype=bool)
 
     def selecting_mouse_move(self, event):
         """Handles the mouse moving when the tool is in the 'selecting' state.
@@ -246,12 +246,12 @@ def normal_key_pressed(self, event):
     # ----------------------------------------------------------------------
 
     def _dataspace_points_default(self):
-        return empty((0, 2), dtype=numpy.bool)
+        return empty((0, 2), dtype=bool)
 
     def _reset(self):
         """Resets the selection"""
         self.event_state = "normal"
-        self._active_selection = empty((0, 2), dtype=numpy.bool)
+        self._active_selection = empty((0, 2), dtype=bool)
         self._previous_selections = []
         self._update_selection()
 
@@ -279,7 +279,7 @@ def _update_selection(self):
             return
 
         selected_mask = zeros(
-            self.selection_datasource._data.shape, dtype=numpy.bool
+            self.selection_datasource._data.shape, dtype=bool
         )
         data = self._get_data()
 
diff --git a/chaco/tools/pan_tool.py b/chaco/tools/pan_tool.py
index 61f2e28bd..66a4e9ae4 100644
--- a/chaco/tools/pan_tool.py
+++ b/chaco/tools/pan_tool.py
@@ -231,8 +231,10 @@ def panning_mouse_move(self, event):
                     newlow = mapper.map_data(screenlow + screen_delta)
 
                 # Use .set_bounds() so that we don't generate two range_changed
-                # events on the DataRange
-                mapper.range.set_bounds(newlow, newhigh)
+                # events on the DataRange.
+                # Do an explicit conversion to float because raw values may not
+                # be floating-point types, which makes NumPy unhappy (#854).
+                mapper.range.set_bounds(float(newlow), float(newhigh))
 
         event.handled = True
 
diff --git a/chaco/tools/tests/test_data_label_tool.py b/chaco/tools/tests/test_data_label_tool.py
index c4deabb85..1f40c55af 100644
--- a/chaco/tools/tests/test_data_label_tool.py
+++ b/chaco/tools/tests/test_data_label_tool.py
@@ -10,7 +10,7 @@
 from chaco.api import ArrayPlotData, DataLabel, Plot
 from chaco.tools.api import DataLabelTool
 
-IMAGE = np.random.random_integers(0, 255, size=(100, 200)).astype(np.uint8)
+IMAGE = np.random.randint(0, 256, size=(100, 200)).astype(np.uint8)
 RGB = np.dstack([IMAGE] * 3)
 
 
diff --git a/ci/edmtool.py b/ci/edmtool.py
index 118ec605a..dbd8ddb1f 100644
--- a/ci/edmtool.py
+++ b/ci/edmtool.py
@@ -77,7 +77,8 @@
 import click
 
 supported_combinations = {
-    '3.6': {'pyside2', 'pyqt', 'pyqt5', 'null'},
+    '3.6': {'pyside2', 'pyqt5', 'null'},
+    '3.8': {'pyside6', 'null'},
 }
 
 dependencies = {
@@ -95,7 +96,7 @@
     "swig",
 }
 
-pypi_dependencies = {"sphinx-copybutton"}
+pypi_dependencies = {}
 
 # Dependencies we install from source for cron tests
 # Order from packages with the most dependencies to one with the least
@@ -111,6 +112,7 @@
 
 extra_dependencies = {
     'pyside2': {'pyside2'},
+    'pyside6': {'pyside6'},
     'pyqt': {'pyqt'},
     'pyqt5': {'pyqt5'},
     'null': set()
@@ -118,7 +120,8 @@
 
 doc_dependencies = {
     "sphinx",
-    "enthought_sphinx_theme"
+    "enthought_sphinx_theme",
+    "sphinx-copybutton",
 }
 
 doc_ignore = {
@@ -161,6 +164,7 @@
 
 environment_vars = {
     'pyside2': {'ETS_TOOLKIT': 'qt4', 'QT_API': 'pyside2'},
+    'pyside6': {'ETS_TOOLKIT': 'qt4', 'QT_API': 'pyside6'},
     'pyqt': {'ETS_TOOLKIT': 'qt4', 'QT_API': 'pyqt'},
     'pyqt5': {'ETS_TOOLKIT': 'qt4', 'QT_API': 'pyqt5'},
     'null': {'ETS_TOOLKIT': 'null.image'},
@@ -204,7 +208,7 @@ def install(runtime, toolkit, environment, editable, source):
         | ci_dependencies
     )
 
-    if toolkit == "pyside2":
+    if toolkit.startswith("pyside"):
         addn_repositories = "--add-repository enthought/lgpl"
     else:
         addn_repositories = ""
diff --git a/pyproject.toml b/pyproject.toml
index b1256a319..26b1ea674 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,5 +1,5 @@
 [build-system]
-requires = ["cython", "oldest-supported-numpy", "setuptools", "wheel"]
+requires = ["cython", "oldest-supported-numpy", "setuptools<65.2", "wheel"]
 build-backend = "setuptools.build_meta"
 
 [tool.cibuildwheel]