Purge merely removes configuration files in addition to doing what remove does, it doesn't completely wipe paths.
When you do this, do you see anything unusual in your apt install output? Under the hood, these postinst scripts get run on installation to manage the symlinks needed for FreeCAD to work:
https://salsa.debian.org/science-team/f ... 3.postinst
https://salsa.debian.org/science-team/f ... 2.postinst
Code: Select all
update-alternatives --install /usr/bin/freecad-daily freecad-daily /usr/lib/freecad-daily/bin/freecad-python3 30 \
--slave /usr/bin/freecadcmd-daily freecadcmd-daily /usr/lib/freecad-daily/bin/freecadcmd-python3 \
--slave /usr/lib/freecad-daily/lib freecadlib-daily /usr/lib/freecad-daily-python3/lib
So it tries to create a symlink at /usr/bin/freecad-daily, /usr/bin/freecadcmd-daily, and /usr/lib/freecad-daily/lib. After removal, those files should not exist, and if they do, the postinst script will fail, resulting in a broken installation.
As far as I can tell this problem keeps popping up because people are sometimes given the advice to install things in system paths like /usr/lib/freecad-daily/Mod, and then when the system tries to do something to what should be a system-managed location, it fails because it detects the user has modified it and isn't sure how to proceed safely. If this is happening from other workflow, there's a bug, but nobody has indicated such a workflow for me to investigate.