I recently built a computer back in December with an RX 6800, an x570 ROG motherboard, and a Ryzen 3700x. The GPU is amazing in almost all of the titles I throw at it, but the moment I boot up Destiny 2 and try to do anything from going to the tower to playing crucible, the FPS jumps from 50 to 80, and if I cast a super, it goes all the way down to 30, all on the lowest settings possible. I believe this is a driver issue and it would be great if at some point there will be a driver update for this game.
There has been a long history of optimization issues with AMD drivers and this title. What you can try is to install the 20.4.2 driver and see if that works. Sure, it doesn't officially support the 6000 series and may have negative impact in other titles, but you can give it a shot and see if it fixes at least the low FPS issue.