Well, I would suggest no longer building any OS for this device, there doesn't seem to be enough interest to run this OS, so might as well not spend the time on building updates. I think I'm just going to ditch mine since the hardware designers have very little desire to see it stay operational.
I tried with an hdmi, and still nothing. The system also doesn't try to expand the filesystem to fill the free space. And since the hardware designers didn't bother to include a serial port, can't see what is happening. I'm guessing something with GRUB, but that's a guess at this point. It is definitely something different between kernel v5 and v6, every one of the v5 flavors boot right up as expected.