pdan What about the command for the installed packages: proton and keyring?
The protonvpn command refers to the proton-vpn-cli app. This is a different application than proton-vpn-gtk-app, which you can launch with the protonvpn-app command.
You can try the following:
sudo eopkg it proton-vpn-cli
protonvpn signout
protonvpn signin your_email/username # type password, it won't be visible
The GUI app should then log in using the new account session.