I've build an arduino nano ble board in my V2 goggles that connects to the para bluetooth module in my Frsky X18 transmitter to create a completely wireless setup.
You can talk shit about Frsky all you want but that is something you can't do with a Radiomaster.
The medlindrone setup Bardwell is mentioning is only single axis. If you're looking for a dual axis solution I can recommend the gimbal setup from Motionsic especially for fixed wing fpv.

I'm currently building a modified AOS UL7 EVO with the Heq gimbal to use both with normal stabilisation and headtracking.
With the new position hold function in Betaflight dual axis headtracking has become alot more interesting for quads.

I've seen people making the head tracking thingy to fix on the goggles with an ESP32. But that's all I know.

With the walk snail the goggle connects directly to the gimbal. Is there no analogous DJI solution?

Not fully right, walksnail vtx's connect directly to the gimbal and headtracking with walksnail goggles doesnt go through the FC, it goes directly from the vtx to the gimbal

Off topic, but what is your keyboard? Sounds great, similar to IBM Model M.

Cant we somehow use head tracker built in DJI goggles? With O3 or O4?