I have exactly the same problem with a biostar a870u3 mobo, same system runs OK on a gigabyre ga-890gp-ud3h.
System 5 on biostar will boot OK but won’t shutdown.
I have the latest bios, 11.4 did not have these problems. This powernow-k8 has a history of nasty problems, I wish
someone who knows would fix them. 12.1 is filled with bugs and I “downgraded one system 12.1 back to 11.4”
Maybe time to consider red hat. I’ve used suse since 2 0r 3 and it seems to get more and more bugs. I think their
release cycle is too rigid and forces them to release before ready. The old slackware with kernel 1.0 was the best.
Also some of the bugs NEVER get fixed.