Aye since the advent of DX12 and proper DX12 games coming out no one has bothered with mGPU or whatever it's called at all. We're actually getting console games now, they're barely even 'ports'. I don't even think there is a single DX12 game that works with more than one GPU. I could be wrong about that, but the last time I checked was with two Fury X and it was an absolute nightmare. That was 2015? maybe early 2016. Hardly anything at that time worked with it then.. Wolfenstein - no multi GPU support at all. BLOPS III - support, but artefects everywhere, glitching, "hopping" and black screens. FO4 -
There was also the VRAM issue, and lots of black screens and lock ups because of it. I sold one of my Fury X very shortly afterward and would not touch either now.
I think it's safe for me to categorically say that unless consoles get more than one GPU? it's over. It has been for ages, too.
As far as I know there is, one, singular title that has DX12 mGPU support, and that's Civ6. I think Beyond Earth also applied the same concept via Mantle. This isn't AFR though, it's split-frame rendering, which is useful for a game like Civ, but would quickly fall apart if used for most traditional games particularly ones with fast moving/player following/first person/ect cameras.