TEKKEN 8 is the latest fighting game from Bandai Namco Studios and it worked pretty great on Steam Deck / Linux at release except for online multiplayer - but that should now be solved.
The problem is that online matches would disconnect — every time. Valve looked into it and now a fresh update is available for Proton Hotfix that Valve developer Pierre-Loup Griffais mentioned on X (formerly Twitter):
Image text: "A Proton Hotfix is now live for the Tekken 8 online disconnect issues and is selected by default for the game."
Since it's now set by default, you shouldn't need to do anything but run the game. If you previously forced a compatibility option on it, you should uncheck the box and let Valve switch it over for you. If you don't see it happening automatically you can select Proton Hotfix yourself in the compatibility options.
Where to buy TEKKEN 8: