Foundry VTT (Foundry Virtual Tabletop) is probably one of the absolute best there is for playing virtual table-top games on Linux and there's a huge new release out with a new video to explain the whole thing.
Getting into these can be a little daunting, with so many options within options and lots of different game packs to consider trying out with your friends. Foundry VTT makes it a bit easier though, with a one-time purchase that allows all players to join you free when you host the game as the GM (Game Master). Even better, it's built on Linux — for Linux, as the developer noted before.
The 0.8.6 release of Foundry VTT went out a few days ago, which is an absolutely huge upgrade to the whole thing. I continue to be in awe of what they're able to do with it. Expect markedly improved networking performance with the likes of HTTP2 support, "a comprehensive and standardized Document schema for the API which brings a lot of power to already existing features and adds a lot of new features for community developers", a complete overhaul of the audio engine (using WebAudio API), additions to their graphical systems to allow for overhead titles / lighting improvements. Check out their brand new explainer overview to get an idea of what it's like: