I know for me, at least with gnome, toggling between performance, balanced, and battery saver modes dramatically changes my battery life on Ubuntu, so I have to toggle it manually to not drain my battery life if it’s mostly sitting there. I don’t know if Mint is the same, but just throwing out the “obvious” for anyone else running Linux on a laptop.
It looks like there are instructions here about hosting your own flatpak instance: https://docs.flatpak.org/en/latest/hosting-a-repository.html