HUD glasses kind of suck since having a display oriented to your head is uncomfortable. Adding 3DOF tracking only partially solves that, so you go 6DOF to maximize optical/vestibular comfort. Now you're rendering a virtual display within a virtual environment, but look at all that wasted space! So add more virtual monitors! Now you need some mechanism to manage them, so you add that and now you have a windowing system... so why are you rendering virtual monitors with fixed space desktops when you can just be rendering the application windows themselves?

The best portable private display for your laptop will inevitably be a 6DOF tracked headset with an XR native desktop.

Yes sorry about my excessive use of French in the comment, I didn't mean it has to be a fixed 1:1 slab of the realspace screen, desktop app windows in XR space would be ideal, but none of the products seem to be able to get it all right yet.

Apple's visionOS comes close but it's crippled by the trademark Apple overcontrolling.

Then this is actually much closer than previous headsets?

There is a lot going on to render the desktop in a tracked 3D space, all that has to happen somewhere. If you're expecting to plug a HDMI cable into a headset and have a good time then I think you're underestimating how much work is being done.

OpenVR and OpenXR are really great software layers that help that all work out.

I am currently writing this from an xreal one pro. I think it fits what you are asking for.

I don't understand your comment. What you're describing has existed for years.

Well maybe not compatible with MacBooks then, with just a USB-C plug-and-play experience? or I presumed it didn't exist

When I look up the actual release dates on viable head mounted displays, it turns out I'm wrong: not years, more like "year."

You should check out the xreal one!

There you go https://www.sightful.com/

My Viture AR glasses are just a dumb display with an accelerometer, and work extremely well.