Now, PYTHON_TARGETS and PYTHON_SINGLE_TARGET are set to 3.10. Gentoo is not yet ready for python 3.10. I had to disable 3.10 and enable 3.9 in /etc/portage/package.use. Reproducible: Always
Gentoo is ready apart from a small number of packages. You're going to have to be more specific about what your issues were.
At least, x11-wm/xpra was affected. I will come back with more.
(In reply to amano.kenji from comment #2) > At least, x11-wm/xpra was affected. I will come back with more. Then see bug 853619.
After removing x11-wm/xpra, this issue disappeared. *** This bug has been marked as a duplicate of bug 853619 ***