You can use the decky XR gaming plugin to get 3 dof virtual display on steamdeck with XR glasses like the Xreal, Viture, Rayneo, and Rodkid glasses.
I’d like a pair of glasses that are nearly dumb, just an HDMI/DP/USB input and tracking head movement. Is that what this is doing?
There’s a bunch of these xr glasses that are just a display and a gyro, no cameras, no Wi-Fi, no phoning home. I’d go with Viture at this point, XReal has been super shitty about working with third parties, Viture has a Linux sdk. Look for a sale, maybe Black Friday. If you buy a pair for $400 you’ll probably be disappointed. $100-200, maybe more reasonable.