Neat. I (occasionally) use emacs in a trivial node.js-as-compositor stack on a Lenovo Explorer on linux. With a 7px font, a pixel-aligned window, no temporal supersampling (because low fps on an old laptop's integrated graphics), and WMR's handwave 500px-ish diameter pixels-not-blurred-together region, it's bearable, but far from competitive with a 1080p laptop screen. With subpixel rendering (Explorer has normal non-PenTile subpixels), a 5px font is ok (but not in emacs), but only across say 300px.

With better lenses and a better panel, an HMD might be competitive. But it's not perceived to be market, and there's pervasive confusion about the (minimal) GPU and (slow) fps needed. And there's only limited diy infrastructure.

But I enjoyed live-coding a vr environment (hot loading three.js and react.) At least with desktop mirroring, to flip-up to screen when the world broke.

Perhaps https://pharojs.github.io/ ? Croquet Project, Open Cobalt, and OpenQwaq are all dead, and 3dicc seems to have gone closed-source commercial. Ah, ST - feels like the 1980's all over again. :/ But https://github.com/ronsaldo/woden looks alive. And someone apparently hacked a bridge to Unreal. I wonder what else is out there?