Thanks for the advice, everyone! I’m using rsync to back up my home directory on the Deck right now, and I’ve migrated a lot of my smaller games I’ll want to have access to on both the Machine and Deck to a 256 GB microSD I had lying around (including my RetroDeck setup). I’ve also flashed the SteamOS installer onto a thumb drive.

I think I’ll plan to just try putting the Deck SSD into the Steam Machine and see if it boots up and runs properly or not. If it looks like there’s any issues, I’ll just reinstall SteamOS on it and restore some of the files I’ll want to from the backup external drive.

Then I’ll do the same with the SM SSD in the SD, reinstall if anything’s funky, and then copy files from the backup onto it again (though most of those will be mods and such for larger games that’ll just live on the Steam Machine now, so it should be light work).

Just need to make sure to have a list of my Decky plugins in case I need to wipe things and make a list of the Flatpaks I’ve installed.