It might look too long at first, but it’s really simple. I did it with the SD card part as well and it worked (almost) flawlessly. The only problem I encountered was first launch of battle.net in game mode - nothing would happen, loading was taking forever. I then tried it in desktop mode and the game ran. Went back to game mode and since then everything works without any hiccups.
I followed the text guide here: https://overkill.wtf/how-to-install-the-diablo-iv-beta-on-steam-deck/
It might look too long at first, but it’s really simple. I did it with the SD card part as well and it worked (almost) flawlessly. The only problem I encountered was first launch of battle.net in game mode - nothing would happen, loading was taking forever. I then tried it in desktop mode and the game ran. Went back to game mode and since then everything works without any hiccups.