Total War: WARHAMMER III has just been formally announced by SEGA / Creative Assembly and the good news is that porter Feral Interactive have right away confirmed it's being supported on Linux (and macOS).
"The cataclysmic conclusion to the Total War: WARHAMMER trilogy is coming. Rally your forces and step into the Realm of Chaos, a dimension of mind-bending horror where the very fate of the world will be decided. Will you conquer your Daemons… or command them?"
For the Linux release date, usually it's a little while later but in this case it seems Feral may have been pulled in earlier than usual as Creative Assembly noted it will be available "as close to launch day as possible" with the exact date to be confirmed closer to launch which will be this year 2021. They also confirmed that it will be on the Epic Store but this time (like TROY did) it's not going to be exclusive at all.
What races will be in it? Creative Assembly mentioned it will have "a wider selection of individual races than any previous Total War: WARHAMMER core title" and "the four Ruinous Powers of Nurgle, Slaanesh, Tzeentch, and Khorne prepare for war and two mighty kingdoms stand sentinel: the stern warriors of Kislev and the vast empire of Grand Cathay".
Once we get more confirmed features and info we will let you know.
You can wishlist / follow on Steam. You can pre-purchase which gives an additional free Race Pack that more details will be given on "soon".
Update: Feral Press replied to our question about cross-platform online support, as traditionally their ports are locked for Linux/macOS together and Windows by itself. Here's what they said:
We do not have anything to announce in regards to the support of the cross-platform multiplayer.
Should the situation change, we will make an announcement on our official site and social media channels.