Blackbird

ARM-based machines also tend to lack upgradability and expandability, and, unfortunately, ARM is going through its own gradual lockdown regarding higher-performance devices.
Fortunately this mostly doesn’t happen on recently mature ARM64 machines. This should be common only on older 32-bit ARM devel boards.
So my IceOS project will be started on ARM64, PPC64, PPC64EL machines.
I will also help to port Parabola, PureOS, GuixSD, LibertyBSD onto ARM64, PPC64, PPC64EL.

Check out the specs; you'll see that it contains "1 HDMI Full HD (2D) video port"

My understanding is that this is from an AST2500 (based on https://www.phoronix.com/scan.php?page=news_item&px=Raptor-Blackbird-Details)

It seems to be part of the BMC, and my understanding is that the software running on the BMC firmware is free. Because Raptor says it "ships with fully open and auditable BMC firmware, based on the Open BMC project." I have not audited that to confirm it though.

But, one will need at least version 4.11 of the kernel:
https://www.phoronix.com/scan.php?page=news_item&px=ASPEED-AST2500-DRM-4.11

And yeah, it seems to be quite a different architecture when the same thing that e.g. controls the fans also does your video...

Yes, it does seem it's unaccelerated [0] but there's at least HDMI onboard. And don't forget there are also PCI Express slots. But that means going to back to proprietary firmware junk again with a discrete card. So, it seems people will have a choice to make on their freedom. I'll opt for unaccelerated graphics.

[0] https://wiki.raptorcs.com/wiki/Troubleshooting/GPU has:

KDE is laggy with the AST VGA GPU

KDE's default compositor uses OpenGL. This makes sense when 3D GPU acceleration is available, but when using a simple unaccelerated 2D GPU like the AST VGA GPU, the result is that 2D operations get converted to 3D operations by KDE's compositor and are then converted back to 2D by llvmpipe, which introduces significant overhead.

To fix this, go to System Settings → Hardware → Display and Monitor → Compositor, and select XRender as the Rendering backend. You'll probably also want to select Smooth (slower) as the Scale method (it's still much faster than OpenGL, and it looks quite a bit better).