私、気になります！
I don’t get it, honestly.
Just do split tunneling, and exclude a secondary browser or something. Way better setup, IMO.
Plus, you don’t need to search for tons for extensions, which might not be official/trusted; and it’s better to have a backup browser anyway.
Mint with Gnome/KDE/other DE?
I’d recommend Shelter over a regular user, so you won’t have to switch between them; but it works too, if you prefer it this way.
Have you tried creating another ‘profile’ (user)?
I’ve used banking apps on LOS and GrapheneOS, it worked great and never complained.
I mean, split tunneling is a feature most VPNs supports, so why work harder for worse setup.