Update as of 19th October, 2022: you should swap to Prism Launcher which is a drop-in replacement for PolyMC.
Want to get Minecraft working easily on Steam Deck or a normal Linux desktop without much fuss? Here's one way you could do it and it makes it easy. For this I picked the PolyMC launcher (a fork of MultiMC) available on Flathub, as the current official Minecraft launcher Flatpak doesn't save your password on Steam Deck and PolyMC of course deals with modding too.
Here's a recent video guide for you, with text steps below:
You will find this video also on the Steam Deck section of the PolyMC Wiki!
- Install PolyMC from the Discover Software Centre on Steam Deck, or Flathub directly for desktop Linux.
- Launch PolyMC and add your account in the top right corner. It supports both Mojang and Microsoft logins.
- Go into the main PolyMC Settings, click Minecraft in the left panel and click the option to close PolyMC when the game window opens. Otherwise, loading in Game Mode / Deck UI on Steam Deck it will flicker between the two windows.
- Ensure in the PolyMC Settings that Java is set to the latest version, which is needed for the latest Minecraft.
- Click Add Instance in the top left, then pick either normal Minecraft or find some mods with the built-in search and it installs everything you need for you.
- To be able to launch directly from Steam: go to the Games menu up the top -> click add a Non-Steam game and then find PolyMC in the list.
Some YouTube comments suggested trying out some optimized modpacks, but really I didn't see a big enough difference in terms of performance or power use to make them actually worth it on Deck compared with vanilla Minecraft when testing on the same map seed. Controller mods were also suggested, but they're rarely updated and often only work with specific Minecraft versions so sticking with Steam Input and just adjusting a few keys is the best choice for that. Update: how to get Steam Deck and Gamepad controls in Minecraft.
You can find many more Steam Deck guides on the GamingOnLinux YouTube.