SteamOS Recovery Image Can Restore Your Steam Deck But Won't Help Your Toast Game
Unlike a true gaming "console" handheld such as the Nintendo Switch, Valve's Steam Deck is essentially a portable PC more akin to the Aya Neo or various GPD devices. This is great from a certain perspective; it means that when things go wrong, you can usually fix them. Unfortunately, it also means that it's a lot more likely that things will go wrong to begin with.
In the case that you wreck your Steam Deck's SteamOS install, don't panic; Valve has released a recovery image for the Steam Deck. It's a fairly simple process where you write the image to a USB flash drive and then boot to it on the Steam Deck. From there, you have three recovery options, as well as the ability to use the recovery image to repair your existing install, if you have the skills to do so.
The recovery options include simply reinstalling SteamOS (preserving your games and content), clearing all your local user data while leaving the operating system intact, or completely wiping the system and doing a factory reset. No matter the state of your Steam Deck, as long as it's physically and electrically intact, one of these options will probably get you going again.
It's worth noting that Valve is probably using the "toaster" word literally to refer to smart toasters here, not figuratively to mean "a very slow computer." SteamOS 3 is based on Arch Linux, and in theory should be able to run just about anywhere the x64 builds of Arch Linux run, which is to say just about any desktop or laptop PC in the last ten years.
That doesn't say anything about game compatibility, of course, but some titles, such as Elden Ring, have already been found to run better on Linux with Proton than on Windows. It's not unimaginable that in the future, folks could keep Windows around for professional or creative work while booting into to SteamOS to play games.