I’m not able to install OpenBSD 6.9 on my Intel NUC i5. It’s a few years old so I’m kinda surprised that OpenBSD will not boot from USB or boot once installed. I managed to find a couple of references and while I thought I wrote about it already I’ll just copy my latest notes here.
First you’ll need a machine/OS that can read the partition on the USB. This can be a challenge if you try a stock Windows or Mac. I had to use a previously installed FreeBSD machine.
bootpartition on the installed HDD or SSD
That should do it. (knock on wood)