I already had KiCad installed, so I uninstalled it to see how long it would take. It took me 51 seconds to clone the repo and reinstall KiCad. I thought this wasn't too bad.
But the joke was on me — when I tried to open the PCB file, KiCad said: "KiCad was unable to open this file because it was created with a more recent version than the one you are running. To open it you will need to upgrade KiCad to a version dated 12/29/2024 or later."
So I now think your position is reasonable. Also I think I need to upgrade Debian.
KiCad sounds to me like a great target for a project based Nix Shell install.
Always have the right version for it "locked". It works well with most tools except those that save stuff in the .config folder as it messes up isolation.
If you find the nix language daunting, for basic stuff like nix shell setup its easy but also LLMs are good for it.