How to install extra software, apps and games on SteamOS and Steam Deck

The Steam Deck with SteamOS (and other devices that will ship with SteamOS) use a locked-down filesystem, so installing extra software is a little different. Here's what you need to know in a simple to understand guide.

Unlike traditional Linux distributions (like Ubuntu) you don't install packages system-wide, as the operating system files are locked and replaced on system updates.

Instead, SteamOS out of the box supports something called Flatpak. It's a type of Linux packaging that's supported across many different Linux distributions. For SteamOS, it uses Flathub by default as the list of supported packages. So if you search on Flathub, and it's available, you'll be able to install it! This is useful to know because it means when away from your SteamOS system, you can visit Flathub directly and search any time.

To do this on a SteamOS system you'll need to boot into Desktop Mode via the Power menu. Picture examples are from a Steam Deck with SteamOS 3.6:

Note: in Desktop Mode, you'll have a shortcut on your Desktop named "Return to Gaming Mode" to go back to the main Steam Gaming Mode interface.

Once in Desktop Mode you're going to want to search for an app called Discover. Do this by tapping the bottom left button to open the menu on the desktop:

Hint: On a Steam Deck in Desktop Mode you can press STEAM + X to bring up an on-screen keyboard.

Note: anything installed in Desktop Mode will also need you to run the updates for it manually in Discover too. It's not automatic when in the main Gaming Mode. So remember to check back on it often. Example below shows many updates waiting in the Desktop Mode.

The updates page may at times list lots of packages, some with the same name, these are special runtime updates for the apps you install to allow them to continue working.

Before searching for any new software though, we should probably check just to ensure Flathub is actually enabled. The settings page should just look like this:

You're now fully good to go.

Inside Discover you can search for whatever you want, and it looks it up on Flathub for you. In the example below I'll search for and install the classic Space Cadet Pinball. When you click on an app, the Install button is in the top right.

Once installed, the Install button changes to Launch.

What about if you want to access what you've installed in Desktop Mode inside the main SteamOS Gaming Mode? That's also thankfully very simple! You can find it in the bottom left app menu, hover over it and right click -> Add to Steam.

After you've done that and booted back into Gaming Mode, it will appear in the Non-Steam part of your Steam Library. Go to your Library, and scroll along to Non-Steam at the top.

SteamOS does also support AppImage. So if you find an app or game that supports Linux systems, and has an AppImage available for download (usually named like "Title.AppImage"), you should be able to use that too. That will be different for each individual app.