(This particular one uses USB-C for video input, but they also sell an HDMI adapter for it.)
Of course, in practice it's just a display and can be used for any purpose. I do appreciate the fact that you don't have to mess around with all the usual VR setup chores with these - it's really very plug and play.
FWIW despite the weird name that invokes cheap Amazon noname brand vibes, these guys have been around for a few years now. They do have other headsets that are in the same ballpark price-wise as XREAL, too - e.g. GOOVIS Young, which is pretty decent for on-the-go use with a smartphone etc. I've owned that one for three years and used it many times with no issues before splurging on G3 Max.
And yeah, $1K is quite a lot, but the 65 degree FOV and 2560x1440 (per eye) OLED that you get for it really does look amazing - I haven't regretted that purchase in the slightest. It's rather bulky, though, although still nowhere near as heavy as VR headsets. Still, not something I'd want to carry on the go.
I hope we'll get 4K per eye some day with this tech. Whichever brand does it first for reasonable $$$, it'll completely replace my primary display.
XREAL as well as some drone FPV goggles support non-/partially-head-tracked HDMI input, albeit with much smaller FOV for comfort reasons.