When using the Kotlin multiplatform generator, there will be a "HttpBasicAuth.kt" file containing the following import
import io.ktor.util.InternalAPI
which needs to be removed or updated to
import io.ktor.util.io.InternalAPI
when using ktor 3.0.0-beta. Using this beta version is required for wasmJs support on Kotlin Multiplatform, so unfortunately I cannot downgrade to a stable version.