Just to comment on thoughts like "the yeast doesn't contribute much flavor"
Beer can be a very simple product with yeast being 1 of the 4 main ingredients. In my experience, every yeast adds character to a beer. Maybe that is esters/aromas/flavors, or maybe that is mouthfeel, or sweetness, or sulfur, or etc. London Ale III adds character to a beer. US-05 adds character to a beer. W-34/70 adds character to a beer. And yes, all Kveik strains add character to a beer.
Can you make a good Oatmeal Stout with Voss, Lutra, Tormodgarden, or another Kveik strain? Very likely. You may need to tweak the recipe toward the yeast selection. I do wonder if you can make a Stout with Lutra and tell it apart from one made with US-05. That is somewhere on my list of things to check out. That said, if I was going to make an Oatmeal Stout, I would look towards an English style ale yeast.