The CircuitPython 4.0.0 has just been released, and it does include support for µGame. However, due to last-minute breaking changes in RC4, and my travelling that made it impossible to fix it over the weekend in time for the release, the Stage library is broken in that release and won't work.

So please refrain from upgrading for now.

I'm being told that there should be a version 4.0.1 released next week or so, which will have it all fixed.