Looks like both require python-mutagen which is not available for Sparky 6/Debian Bullseye any more (repalced with python3-mutagen).
I build exaile myself so I will try to rebuild it with python3-mutagen.
Nicotine++ is an old package, no upgraded for long time so works on older libs, means on Sparky stable now, so can't fix it on Sparky 6, sorry.