Proton are deleting the protonvpn-cli pkg shortly.

For users wishing to continue to use the service there's a process here:
https://protonvpn.com/support/linux-openvpn/

The only modification to the linux generated openvpn conf files is the location of the dns resolve files.
They're here:
up /usr/local/etc/openvpn/update-resolv-conf
down /usr/local/etc/openvpn/update-resolv-conf

The 'update-resolv-conf' linux pkg isn't required.

Regards,

Steve