It was a tough start for Minecraft Legends on Steam Deck at launch, with it not actually launching on Steam OS.
Fortunately, the community is quick to put the bug fixes and data Valve needed to identify the issue, and this morning, we got a Proton Hotfix to fix the issue and the game now runs with no compatibility.
You should get the latest Proton hotfix automatically, but if not, search for it on your Steam Deck and install the latest update
If you run in game mode, you may have some issues linking you account, we recommend you run the game in Desktop mode to link your Microsoft account, otherwise you will need to back out and restart each time it freezes on the load screens, to progress.
In-game, the tutorial runs a perfect 60 FPS, but once you git the main game, you will start dropping into the 45-60FPS range, so we recommend you drop it down to Medium settings and this will hold a perfect 60FPS everywhere
We do have the Cryo Utilities changes and UMA buffer fixes in place from our video below that might also be helping our performance