Have you tried to clone the forked DisplayCAL repo and start it from there?
Following those steps to make sure all dependencies are locally installed:
- Installing DisplayCal via pip on Ubuntu 22.04 based distros (KDE Neon). - #5 by Brian_Innes
- and maybe this: ubuntu 22.04 · Issue #284 · eoyilmaz/displaycal-py3 · GitHub
At least the last time (like 6 months ago?) I started it from the cloned repo worked for me well.