If you had it working on Pi... would it be "headless"?
Afaict, there are about 5 functions that must be called to launch EGL in "headless" mode. This is a trivial issue, these functions can be added to LWJGL in an afternoon. Or even called via dyncall without bindings.
The main problem is, as I said in the LWJGL forums, handling input without X. Keyboard, mouse, controllers, touch, we'll need something to handle all that. We cannot use GLFW, it supports 3 backends (X11, Wayland, Mir) and even though Wayland is supposed to be a lightweight solution (and works on RPi afaik), I think you'd want to avoid that too. So we'll have to go low-level. This is probably not that big of a deal, I mean, the main problem is identifying the APIs we need bindings for. Once we know how it's done, adding the bindings to LWJGL is going to be quick.
Which brings me to; I don't own an RPi and I don't know when/if I'll have time to do the above research. The easiest thing for me would be to get a list of APIs to add to LWJGL, from someone that knows what's necessary.