crashes shortly after starting (probably when it tries to load some python script). PYTHON_SINGLE_TARGET="python3_8" emerge -1 hexchat fixed it for me
I am currently cleaning up the open bugs for net-irc/hexchat after having taken over the package. Is your issue still present? With hexchat being two minor versions ahead of when this issue was reported, I assume this might have been fixed if it is an upstream bug.
Looks like it is fixed, it works with python 3.10 here
Closing as obsolete, since the issue seems to have gone away with newer versions of the software and dependencies.
FTR, the issue was discovered on other operating systems as well and has been fixed upstream: https://github.com/hexchat/hexchat/issues/2528