With extra time while in quarantine I idly tried to install 6.6 on an older iMac I have.
Using install66.fs on a USB flash drive, when starting (holding ALT key) it was offered as a boot disk choice. It reaches the boot> prompt, then reaches the "entry point at..." and crashes (machine restarts) after a few seconds with no further messages on screen (transcript below) If I enter "boot -c" at the boot> prompt, the machine never restarts but hangs indefinitely at the same point. I found a post on r/openbsd that seemed sorta similar, and claimed to be resolved by installing 6.4, then upgrading from there but keeping the bootx64.efi from the 6.4 release. However on my machine the 6.4 installation had the same behavior. I didn't try anything older. Is this machine known to work/not work or can I provide any more info to debugging? probing: pc0 mem[572K 64K 3046M 40K 16K 56K 288K 4M 316K 16K 48K 32K 1M 196K 32K 4M 5M 3M 148K 40K 1024M] disk: hd0 hd1* hd2* >> OpenBSD/amd64 BOOTX64 3.46 boot> boot -c cannot open hd0a:/etc/random.seed: No such file or directory booting hd0a:/6.6/amd64/bsd.rd: 3732172+1537024+3885432+0+598016 [376562+128+455] 544+303577]=0xa648d0 entry point at 0x1001000 (hangs here, or restarts machine after a few seconds if not "boot -c") Regards, Allan Footnotes:  https://everymac.com/systems/apple/imac/specs/imac-core-2-duo-2.0-20-inch-aluminum-specs.html  https://www.reddit.com/r/openbsd/comments/eggg4m/64_works_perfectly_but_6566_bsd_kernel_frozen_on/