I think there is something wrong with either your config or they fucked the game optimization. I have played the finals on 1440p on a fucking gtx 1070 and easily got 100 fps. You should be getting much more on 1080p on a 6800xt.

Have you used something like psensor to get a graph of CPU/GPU/RAM usage and temps so you can get an idea of whats going on.

I cannot recommend buying a new GPU at the moment and upgrading from a 6800xt seems absurd.

You mention several SSDs. Are you using a shared M.2 slot?

Some motherboards can have M.2 slots that share pci lanes with the GPU slots. If they are used, it will SEVERELY cut down on the PCIe lanes allocated to the GPU. Make sure this isn't happening.

Does your monitor support VRR?

Your setup should deal quite nicely with almost anything, so unless the performance problem is software-related, I'd just go straight for a more powerful GPU.

But, the 6800 is perfectly adequate, and buying a GPU sucks atm. So to improve your experience, I'd look at making sure the right amd driver is in use, that resizable bar is enabled in your bios, that you don't have a thermal issue, and getting VRR going if you haven't already.

Completely eliminating FPS ever dropping below a desired rate is near-impossible except by significantly exceeding the system requirements to get the FPS you want 99% of the time. You're always gonna have those 1% moments in games where there's just too much on-screen for the rendering to keep up. VRR makes sure you feel those drops as little as possible.

If you're already using VRR, and are sure you don't have a software problem, only then would I look at a GPU upgrade.

But, if you aren't using VRR, consider getting a monitor with FreeSync (If you don't already). IMO it has a much better cost/benefit ratio in terms of the actual gaming experience, than simply going overkill on the CPU and GPU.

You could also try overclocking your GPU. LACT is the linux program you want for fiddling with AMD GPUs. It can tell the resizable bar status and control the fans, too.

If there's any bottleneck, it's your motherboard itself, since it only supports PCIe3.

However, even PCIe3 should be able to get you better frames than that with your hardware, especially on Low. I suspect poor optimization of The Finals, which is unfortunately common with AAA games these days.

I don't think you need to get new hardware, I think you need to figure out if there's something you can do via the Launch Options. Have you checked ProtonDB?

Have you explored your GPU and CPU and memory utilization? On Linux, mangohud is a great tool for this. Verify which component is bottlenecking you performance, you may see something happening when your performance drops.

If something is visible, you may want to target it for an upgrade. If not, something else may be an issue. You may also compare with a fresh setup of nobara just to rule out any misconfiguration or other driver related issues?

Some other mentioned you should be able to run this game without issue, some tips when this happens:

1. Check protondb for the game you're playing and see if there are any good optimization tips people have shared there. Looks to be some for this game.
2. Install and use Game mode
3. Make sure your CPU and Memory are at the most compatible frequencies FIRST (look this up), then optimize from there. You may be getting stutter on cache context switching under wine/proton
4. Don't always use the most recent version of proton, use the most compatible for the game you're playing. You can change this for each game under steam settings. See #1 to find out what most people are saying about performance under different proton versions.

I honestly don't think you need an upgrade, just some optimization.

You could Sidegrade to a x3d chip from AMD, though not sure how CPU-heavy the Finals is. And then there's the upgrade to a new GPU (with accompanying PSU upgrade, maybe/probably). The 6000 series is two generations old now. That would be the most obvious route. RAM and MoBo look fine. How's the fan setup for the case?