I am using Ubuntu 22.04, and I followed the official instructions https://protonvpn.com/support/official-ubuntu-vpn-setup/ for install and later uninstall the app. Now I want to reinstall it again, but after mounting the deb package the proton VPN mirror does not exist when apt-get updating. I cannot find it in the source.list.d folder or source.list file either. Any help is more than welcome, thanks in advanced.
I see I can do it with synaptic package manager, just type what you need in search end select ‘mark for reinstallation’;
maybe this will be easier
I installed the flatpack through Discover (I am using KDE) and it seems to work fine now!
ha! I too have plasma but somehow never thought about the pvpn flatpack in discover 
glad your ok now 
Does this mean it works on steam deck through discover now?
I’ve never used it with steam deck, but if you try it let us know
No biggie. I’ve had it running through a workaround, but anytime I tried the one from the Discover store, the GUI was always just a blank box.