Alright, here’s how to install those things.
Setting up a custom boot animation on Steam Deck is slightly more complex than just accessing a menu option, as you’ll have to dive into the file structure in desktop mode. But it’s quite easy. The main thing is to change a setting on the desktop, create two folders and paste a .webm file. That’s basically it.
As for the OS version, no need to be on 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’ file explorer, similar to Windows Explorer or macOS Finder.
Tap the sandwich icon at the top right of the window and enable “Show hidden files”. (Ctrl+H is a quick shortcut to achieve this as well.)
Create the custom animation folder
After enabling hidden files, navigate to ~/.steam/root/config and create a folder called “uioverrides”. Yes, there are two R’s.
In this folder, create a “movies” folder. You’ll drop in the custom boot video of your choice.
Prepare your video
Custom Steam Deck boot animations require a .webm video, preferably a resolution similar to the Deck’s 1280×800 screen. If it’s not already done, rename the file “deck_startup.webm”. The boot animation will not work otherwise. Also note that Steam Deck startup videos can only be a maximum of 10 seconds long.
All you have to do is restart your deck and enjoy your new animation! If that doesn’t work, review the steps above.
That’s all we can say about it. Now that you know how, install your own favorite Steam Deck boot animation. Beyond the 16 I’ve shared here, more are popping up every day, so go wild.