My fellow HelenOS developer Maurizio Lobardi tested my new display server on a real Raspberry Pi and shared a video of his test. Thanks Maurizio!
Still work to do, btw! Rest assured I am working on it. I've just been quite busy + I stumbled upon a mystEEErious heisenbug. In the end it turns out it's all a case of misunderstanding and misusing async_hangup(). Back to work!