The Package ProtonVPN-gui that I installed with Yast doesn't work with openSUSE
LEAP: I made a support request with ProtonVPN and they replied that ProtonVPN
doesn't support openSUSE at all.
The following is my original request with bug description:

I'm using openSUSE Leap 15.6 with NetworkManager and I want to try the free
version of ProtonVPN, so I installed it via the YaST SoftwareManagement, which
is the usual way on openSUSE.
This is the Proton VPN GUI-Client that was installed:
Proton VPN:     v1.12.0 (library: v3.7.0 / api-client: v0.7.1)

However, I can't get it working, since the client demands credentials that I
don't seem to have. In more detail this is what happens:
I log into the client with my Proton Account. Then I try to connect to some
server in the Netherlands. Then I have to enter my root password and afterwards
my secrets (I assumed this is the OpenVPN / IKEv2 username/ password, I have
also tried the Proton Account password). This is the text of the dialog:
Title: "VPN secrets (openvpn) dialog - KDE Daemon"
Text = "Authenticate ProtonVPN NL-FREE#299142 - Provide the secrets for the VPN
connection 'ProtonVPN  NL-FREE#299142': - A password is required:"
Whatever I enter here, nothing works, the same dialog keeps popping up. I don't
know password I need here other then the ones mentioned above.
Moreover, when I shut ProtonVPN down, my internet isn't working anymore and -
as I found out - DNS was missing, so I always have to delete the file that is
created in the folder "/etc/NetworkManager/system-connections" and reboot.