I installed NordVPN on a SteamOS device so I could watch French TV. They don't have a flatpak, for now I went with enabling devmode and installing the AUR. #steamos#nordvpn
It was a little worse setting this up than I thought it would be. Main problem was DNS wasn't working, which I ended up resolving with "nordvpn set lan-discovery enable"
There's a Proton VPN flatpak too, I'm not too sure what kind of limitations inherent to flatpak might exist in converting their app release.
flatpak flathub support · Issue #965 · NordSecurity/nordvpn-linux
When nord vpn will be provided in flathub as flatpak surfshrak and proton and many others already have there apps in flathub. https://docs.flathub.org/docs/for-app-authors/submission