How to install and uninstall the Mullvad VPN app on Linux.
You can easily add them by following the instructions on their site.
On immutable fedora it can be done via
curl -o - https://repository.mullvad.net/rpm/stable/mullvad.repo | sudo tee /etc/yum.repos.d/mullvad.repo
rpm-ostree uninstall mullvad-vpn --install mullvad-vpn
# after reboot, if not working
sudo systemctl start mullvad-daemon
Is Flatpak, from a technical standpoint, capable of running VPN applications?
Providing .ovpn configuration files would be equally cross-distro, and in fact, would be cross-platform since almost every operating system supports importing OpenVPN configurations or supports a piece of software that does.
I can’t tell you how, because I don’t know the technical details either, but why shouldn’t it be? If given the right permissions it can access the same interfaces as any process.
I ask because to my knowledge, Flatpak applications don't get access to the system interfaces that are needed to control VPN connections. There isn't a portal for it to the best of my knowledge and the way that VPN connections are handled differ between distros.