On Umbrel V<1.0 an installed Proton-VPN with the GUI works fine: A Bitcoin full node in listening mode behind the Proton-VPN.

But on Umbrel V>=1.0 the underlying Linux OS is very restricted and I have not figured out yet, how to install and configure all modules that Proton-VPN needs. There is some issue with storing the credentials:

jeepney.wrappers.DBusErrorResponse: [org.freedesktop.DBus.Error.UnknownMethod] ('Object does not exist at path "/org/freedesktop/secrets/collection/login"',)