Barring from some strange BIOS configuration, it should be fine. In my experience, it's usually when you take an old board and a new-ish GPU that it might be problematic. A BIOS update fixed it in my case. (FWIW, it was an RX 580 on either H61 or B75 board, can't remember which).
Heck, I've used an HD 4650 as a basic display output when I sold my RX 580 and gotten myself a deal on a secondhand 1080, and the 1080 came a bit late due to shipping. Both the 1080 and the motherboard is what I have in my sig below. Works fine, it's just with that pre-GCN AMD cards you need to jump through a few hoops to get proper display (i.e. not 1024x768).
In short, it should be fine. Just be ready to tinker with driver some since Nvidia seems to be laser focused on bringing features to RTX 3000 series rather than taking care of older cards. Kepler (600 series) seems to be particularly finicky with some newer drivers. Even my 1080 had issues with a stable release, but that was solved with a driver update to the next stable release.