To workaround the issue with my HBA, I removed the HBA and did an install to an SSD in a USB 3 dock (Sharkoon)
The OpenBSD installer completed successfully
petitboot doesn't show the OpenBSD partition in the boot menu
If I exit to the OpenBSD shell, I can use fdisk to inspect the SSD and I can see the partition is there. It is /dev/sda4 and type = a6 (OpenBSD)
Is there any way I can get petitboot to boot this partition or does it need some newer version of petitboot or some change in the OpenBSD partitioning scheme?