Ok, here’s how to actually install this stuff.
Setting a custom Steam Deck loading animation is a bit more involved than simply accessing a menu option, as you’ll need to dive into the file structure in desktop mode. But it’s pretty easy. The basic gist is to change a desktop setting, create two folders and place a .webm file. That’s generally speaking.
As for the OS version, you don’t need to be in the beta channel. As long as your Deck is updated to at least SteamOS 3.3.2, you’re good to go.
Reveal hidden files in desktop mode
Switch to desktop mode and open an instance of Dolphin. No, not the GameCube / Wii emulator. Dolphin is SteamOS’s file explorer, similar to Windows Explorer or macOS’s Finder.
Press the sandwich icon in the upper right corner of the window and turn on “Show hidden files”. (Ctrl+H is a quick combination to accomplish this as well.)
Create a custom animation folder
After enabling Hidden Files, open ~/.steam/root/config and create a folder called “uioverrides”. Yes, there are two Rs.
In this folder, create a “movies” folder. There you will play the custom loading video of your choice.
Prepare your video
Custom Steam Deck launch animations require .webm video, preferably similar to the Deck’s screen resolution of 1280×800. If not already, rename the file “deck_startup.webm“. Otherwise the loading animation will not work. Also note that Steam Deck launch videos can be a maximum of 10 seconds long.
All that’s left is to restart your deck and enjoy your new animation! If it doesn’t work, review the steps above.
That is all. Now that you know how, go ahead and install your favorite Steam Deck launch animation. Beyond the 16 I’ve shared here, more and more are popping up every day, so stay tuned.