How To Uninstall ProtonVPN
Solution 1:
You downloaded a deb file. So it can't be in the store.
Proton describes it very clearly:
sudo apt-get install protonvpn
Later in the "notes" they write:
To uninstall the official app:
sudo apt-get autoremove protonvpn
#Remove any leftover files:
rm -rf ~/.cache/protonvpn
rm -rf ~/.config/protonvpn
Seems to be pretty straight forward. (RTFM)