I've considered installing CachyOS on my Deck to be able to use bcachefs for a tiered storage setup with the SD card. For automatic movement of unused files to the SD card over time, because I don't want to deal with managing it myself.
Though I also did the SSD upgrade and haven't really been bothered by space, so haven't bothered. I have that setup on a spare parts PC with HDDs instead of microSD, since that's an older 1/2 TB SSD.
I spent too much time writing a script to do something like this but lost interest/gave up because I really don't swap between games that often and uninstalling/reinstalling was a lot easier.
That said, I do wish Valve would implement something like this first class in SteamOS.
Though I also did the SSD upgrade and haven't really been bothered by space, so haven't bothered. I have that setup on a spare parts PC with HDDs instead of microSD, since that's an older 1/2 TB SSD.