I was in the same boat. I just want the VPN for my torrent client, without it impacting any other running applications/services. Try https://github.com/jamesmcm/vopono, which uses network namespaces and has killswitch functionality.

As for Nix, I have no idea.

I didn’t mention a VPN service. Openvpn is a client/server application, not a service. Vopono is an application that let’s you tunnel a single application through a VPN.

I also don’t disagree with the mod’s reasoning, so… have a nice day I guess.

I just run rtorrent with vopono/openvpn in a tmux sesession on a raspberry PI. It can be a bit of a pita getting utmp working though.