Using SAS bonus points one way and partner flights the other. Is that possible?

Trying to book Oslo to Seoul using SAS Bonus points, but finding dates has been really tough. I’m wondering if there’s any flexibility here.

Is it possible to book one direction using SAS Bonus trips and then use partner airline award availability for the return, all under the same companion ticket? Or does the whole itinerary need to be SAS metal only?

If anyone’s done something like this before or knows how strict SAS is with companion tickets and mixed awards, I’d really appreciate the insight.