There are few others like Hitman, Sniper Elite, Civilization 6.
Some of those may be limited to identical cards though. They basically implemented SLI/Crossfire AFR using DX12.
But effectively there is not much momentum behind it, and many of the big game engines have no support for it so it will not be trickling down to games released under them. No return on development time to target the 1 or 2% of people that might have two GPUs.
A good argument against it would be you could get nearly double the performance of a 1070 with a 1080Ti. And since only a few of Nvidia's top cards still support SLI I can see that trend going away. Nvidia has their Nvlink tech as well. They'll certainly put more R&D into that.
I haven't seen much crossfire stuff in a while, so difficult to get cards, let alone two.