The good news: FreeBSD 2.1 (I couldn't be arsed to download 2.0.5 from the FTP archive so I torrented 2.1 from arcive.org) boots and runs just fine on QEMU.
The bad news; QEMU doesn't emulate a video card this old thing can use properly. I'm wondering how you can talk XF86 into doing 16 grays on a stock VGA.
(Why not VirtualBox? Aside from the even worse video card support for older stuff, VBox only supports PCI network cards, and PCI NIC support is *very* limited in these mid-1990s OSes.)
Something I noticed about this old version of FreeBSD in QEMU is that for whatever reason, it *can't* see the serial or PS/2 ports, even though the most recent release (11.2) sees them just fine.
This is a problem because if I want to get my X11 on '90s-style, it has to be able to see my mouse!
Okay, time to try FreeBSD 2.2.8. I think I'll leave the really old versions to my real 1990s hardware downstairs.
@aatheus Emulated Pentium-class machine in QEMU. I have a real Pentium 100 and a real 486DX2-66 downstairs I can play with it on, but I was a lazy butt this weekend and didn't do it.