Temporalin
According to the documentation, you should be able to https://help.steampowered.com/en/faqs/view/46BD-6BA8-B012-CE43. Unfortunately, I don’t have big enough games to test, and I think it detects that my internet bandwith is higher than the connection to the Deck
It’s probably not worth the risk implied with second hand vs the discounted new unit directly from Valve. You should lower it or just assume you’re not going to sell it
There was Bibliogram but it closed as it was impossible to keep up with Meta’s barriers, sadly
You can install Bazzite and you will have the same experience you would get with SteamOS. Don’t use the extra features and you won’t be able to tell the difference. It is a “just works” experience with minimal setup. The setup even includes emulators and launchers like the FFXIV one so it is even more minimal than SteamOS.
It may not work directly on a given PC or a specific device, but that would also happen if Valve released a generic SteamOS.
Edit: typo
SteamOS uses inmutable partitions, you can’t install things using pacman safely. For OP’s problem my first thought is using a virtual machine or a whole different OS. Maybe there are fonts in Discover/Flathub, which is what SteamOS is designed to use, but I don’t know if that could work.