I have an APU board, trying to describe it:
coreboot build 20160307
4080 MB ECC DRAM
SeaBIOS (version ?-20160307_153453-michael-desktop64)
Found mainboard PC Engines PCEngines apu2
multiboot: eax=0, ebx=0
it has 3 1G ethernet ports, and 4 GBytes RAM.
This has always been extremely hard to get booted. It can't boot from SD card, it is absolutely required to boot from USB (and it is very hard to find a USB device that works). Then, in Linux, it is completely impossible to mount root from USB, even as devices are claimed to be found. The root partition HAS to be on SD Card. And it takes many many repeat attempts to boot, to find the SD card. (An "sdhci" controller is always found, but almost never the partitions on the SD card) Since Linux kernel 5.18, there is no way to mount any root.
What is it?
Is there any Bios that is more reliable?