Bazzite is an alternative operating system for the Steam Deck and for Desktop PCs that closely emulates SteamOS, with numerous additional features and improvements on top. We use immutable Fedora as a base, and allow packages to be layered and kept through updates unlike stock SteamOS. You can even print and change the language from English if you want.
Just make sure it’s mounted in fstab, same as any other distro. If it’s a permanent drive I would mount it to
/var/mnt/ChangeMeInteresting, okay I’ll try it again when I have a chance.