Everyone moved to NextCloud by now

I have not had a problem using ProtonVPN on Linux.

The only VPNs which are not owned by marketing companies are Mullvad and Proton. The largest VPNs are owned by Kape Technologies, renamed because their prior company name distributed malware, whose top people are former Israeli military, so I wouldn’t trust them as far as I could throw them. I would never use a free VPN except for Proton, and Proton’s paid VPN has a lot more nodes and features.