Created attachment 602356 [details] kvirc-9999.ebuild with offending patch removed from PATCHES kvirc-9999 seems to build and run just fine without the patch. It's trivial to remove it from the ebuild, but I've attached a tweaked ebuild anyway. I didn't touch the python dependencies, they may want further munging. #224919 has similar content but it's a decade old; so I presume the current situation warrants a fresh bug report ;)
I already created correct patch about 2 days ago, but porting to cmake.eclass remains... (In reply to Michael Moon from comment #0) > Created attachment 602356 [details] > kvirc-9999.ebuild with offending patch removed from PATCHES > > kvirc-9999 seems to build and run just fine without the patch. No, because upstream migrated from FindPythonLibs.cmake to FindPython3.cmake, which automagically uses newest found Python version instead of version selected by PYTHON_SINGLE_TARGET. So the correct ebuild will override things by passing -DPython3_INCLUDE_DIR and -DPython3_LIBRARY to cmake.
Ebuild was updated in commit 4d91171b612acd924ca814c715634d639b853f47.