Here to add to the "sudden loss in performance" thread:
I have an i9 9900k, 3080Ti (with latest drivers) and 32GB 3200MHz of RAM
Also have 300 hours in Cyberpunk so I am aware of how far I can "push" the graphics as it were. I'm running at 1440p, without RT (though have tried with as well from time to time), DLSS on Quality.
Having just restarted a playthrough and played through all of Regina's missions and the Heist, the Interlude and waking up in the Megatower, I had great performance all the way through, pretty much locked 60FPS. Even with RT on, tho I prefer not to overstress my GPU if I don't have to and the game looks amazing without it anyway (though I do turn it on for the photomode with pathtracing feature)
However, waking up in the Megatower and opening my door, my performance tanked to 30-45FPS, and not a static drop, it fluctuated constantly. So I dropped DLSS to Balanced. Weird that I would have to do that on a 3080Ti, but whatever, I can deal with the small downgrade in visual quality
Still same performance issues. Set DLSS to Performance. Still same performance issues. Set resolution to 1080P with DLSS set to Performance, which my GTX1080Ti back in 2020 could easily do (it didn't even have the DLSS option and didn't need it to render the game at 1080P). Still same performance issues.
My card doesn't get hotter than 65C. My CPU doesn't get hotter than 60C. I have really good cooling options for both, so throttling seems unlikely though obviously I did send a support ticket with my DXDiag log, so maybe they can see something else.
It's really unfortunate because I wanted to get to Phantom Liberty after finishing the prologue, but now I don't really know when to start because I want that experience not to be soured by performance problems.
Small thing to note: After the game updated to Phantom Liberty, I had constant crashes when trying to launch the game from GOGalaxy, so I started it via the executable itself and that worked, but I also had performance problems back then. To fix that back then I removed all the files in my DXCache and GLCache folders in the Nvidia folder in localappdata, and figured that it was just some old cache Nvidia hadn't removed for CP2077 that was causing the issue. But now I'm not so sure anymore.