PyAvrOCD is a GDB server for 8-bit AVR MCUs (see list of supported MCUs and supported boards), enabling you to debug programs running on these MCUs using the GNU Project Debugger GDB. PyAvrOCD communicates with Microchip's debug probes, such as the very affordable MPLAB Snap, and it provides a pass-through service for the UNO-based debug probe dw-link and the simulation tool simavr (see list of supported debug probes).
So, why another open-source GDB server for AVR MCUs? The main intention is to provide a cross-platform AVR GDB server. In other words, it is the missing AVR debugging solution for the Arduino IDE 2 and PlatformIO. In particular, the integration with Arduino IDE 2 is pretty tight, allowing one to start debugging without much hassle (see quickstart guides). Additionally, PyAvrOCD excels in minimizing flash wear and protects single-stepping against interrupts.
PyAvrOCD v1.0.0 has been released. If you would like to give it a try, you are welcome to install it. Any feedback, be it bug reports, crazy ideas, or praise, is welcome.
UPDI MCUs will follow next. I am unsure about Xmegas. One main point missing is an Arduino core for the MegaXU4 chips, similar to MCUdude's MiniCore.