I thought I'd share a small success with installing Debian 12 under VMM, in case some might find it useful. The boot parameters are "install gfxpayload=text console=ttyS0,115200n8". I added these boot parameters from the Debian installer after selecting the Help menu using "H", then selecting "Special boot parameters for special machines." using <F6>.
By the way, I found an article that suggested using "vga=off" instead of "gfxpayload=text". This worked in the installer, but hung up the boot on the post-install, because "vga=off" has been deprecated. This was under OpenBSD 7.4, run from an xterm. Let me know if there are any comments or questions. Cheers, --Bruce