I've been getting into Destiny 2 recently. I have a 4K display and still looks beautiful at that resolution even with 75% rendering scaling. My single AMD RX 470 4GB just can't quite do 4K. Seeing that another used RX 470 4GB is less than $100, I'm trying to determine if Destiny 2 still sees the similar results found here at 4K. https://us.hardware.info/reviews/7854/7/destiny-2-review-benchmarks-on-25-graphics-cards-multi-gpu-s...
As this page's benchmark information is about a year old now.
(I have a OC'ed i5-4670K @ 4.1GHz, NVMe SSD w/ Destiny 2 installed on it and 32 GB of system memory just to outline the rest of my system)
No idea, I would hope that if it was supported it still is. Crossfire at it's best has been a mixed bag of results. Many (probably most) find it not worth it. For every game that works with it well, there are way many more that the dual cards either, doesn't work or it creates an issue that doesn't exist with one card. Hopefully down the line with DX12 and Multi-GPU this gets better, but I wouldn't hold my breath there either.
I would highly recommend you save a buy a single card solution capable of running at the resolution you want.