I also got other tips outside the email list, and this got me going down a rabbit hole within the BIOS. After clearing nvram, and resetting to defaults, somehow this got it to boot up just fine. I'm part relieved that it works, and part concerned that I have no idea why, so I've spent the weekend slowly going through all change permutations in bios to find what's not working. It turns out that disabling com2 specifically (out of 0-3) , breaks... something... on BSD-like systems at least. I'm trying to narrow it down and I'll share in the bug I opened once I have useful info, even if it's naughty hardware.
I'm glad you got yours to work like I got mine to work. My motherboard, a Supermicro X13SAE, only has one COM port. Disabling it caused similar issues as disabling COM2 on yours. Interestingly, I was at least able to boot into single-user mode though, so the bug affected you worse than it did me.
