I don't have a steamdeck (yet) so take this with a grain of salt, but from what I understand it is basically a mini computer running a custom build of Linux on it. So you can install pretty much any kind of software on it that you want, provided it can run on Linux. I believe it's also possible to wipe the drive and install Windows on it instead if you prefer. (Though I've heard proton is pretty good at getting most things to run on SteamOS)