They have an apparently fully working prototype of the endpoint software running on RPI. You can see what @brian says there about status of that, which I’d assume would extend to linux more broadly.
I’m pretty sure one of them also noted somewhere here that they’re making good progress on the headless server.
FWIW, I have similar plans: run the headless server on my new Rockstor (BTRFS-based) NAS, and maybe RPI as endpoint.