> One small disadvantage not addressed is that neither of the two motherboards support BIOS access via COM1, which is a bummer.

I've always wondered if you could burn SGABIOS (https://code.google.com/archive/p/sgabios/) to a PCI(e) card ROM to get this working on real hardware instead of just in QEMU.

Apparently someone did try this, so it might just work: https://www.flashrom.org/User:GNUtoo/Howto_flash_sgabios_on_...

Maybe I should dig up some old flashrom supported NIC card or something.