Assuming you're using Windows, what version are you on? I had issues with extreme drops in framerates with Windows 11 running the game in DX 11 during EA, which I eventually tracked down to a problem with Windows 11 HDR and disabling it solved the problem.

If it's not that, then does swapping between Vulkan and DX11 help, or reducing the graphics settings?

"You may call it 'nonsense' if you like, but I've heard nonsense, compared with which that would be as sensible as a dictionary!"