It's not exclusive to NixOS, but I've only packaged it for NixOS.
The UI looks like shit, but it allows showing all the configs in /etc/wireguard and toggling them on or off with wg-quick.
The biggest issue I had was with slint. I can't make sense of it (yet).
This was written because after getting a windscribe subscription, I found out that the app doesn't work on #NixOS and the pull request to add it 1) doesn't work, 2) is being nitpicked to death.