Distrobox is a way to use pretty much any other Linux distribution in your terminal, along with full GUI apps and now it supports the Steam Deck with SteamOS too.
The update released a few days ago had some issues (#1, #2, #3), which I reported to the developer and they've since fixed up the installers and the documentation for Steam Deck. So with that in mind, I took it for a spin to see how it works and I've been thoroughly impressed with how easy it is.
It gives you a container system to install other distributions. So for the likes of SteamOS on the Steam Deck, without messing with the root filesystem, you can install something like Ubuntu and access everything it has available. Useful for software not available via Flathub (Discover) or elsewhere.
Here's a short video overview of the basic setup and running some apps from Ubuntu on Steam Deck:
Guide (official link):
First up, run these install scripts one after the other in a terminal app (like Konsole on Steam Deck):
curl -s https://raw.githubusercontent.com/89luca89/distrobox/main/install | sh -s -- --prefix ~/.local
curl -s https://raw.githubusercontent.com/89luca89/distrobox/main/extras/install-podman | sh -s -- --prefix ~/.local
Next up, we need to add the directories it uses into our .bashrc file, so we can run commands as normal in terminal. In your .bashrc file (found in your Home folder), open it in a text editor and add these to the bottom:
Now you can install a Linux distribution with Distrobox, with Ubuntu as the example (in terminal again):
distrobox create -i ubuntu:20.04
Then once done, you can enter it:
distrobox enter ubuntu-20-04
This is where the fun begins. Now you can install or do whatever you like, inside Ubuntu. However, you also need to add this to your .bashrc file to run graphical applications / games on Steam Deck: