I initially posted this one on the wrong board, so I apologize for that.
Project information: Input Remapper maps mouse buttons onto keyboard keys.
Name: Input Remapper
Homepage: GitHub - sezanzeb/input-remapper: 🎮 ⌨ An easy to use tool to change the behaviour of your input devices.
License: GNU General Public License v3.0
Upstream has been contacted: yes. Looks like the devs tried some time ago to package IR as a flatpak and failed. It appears to be an issue of permissions. Any Flatpak aficionado here cares to look into this please? IR is an amazing tool! Perhaps Flatseal might help?