On most distros, it's simply named "vkbasalt", you can install it with your distribution's package manager :

Ubuntu/Debian & derivatives :
OpenSUSE :
Fedora :
Arch & Others:

Once installed, you need to create (or edit) the configuration file in :
Pick the text editor of your choice, then paste this configuration :
You can tweak these values, based on my testing, these provide the best results, feel free to comment with your own settings if you think they are better than these.

Once you've done that, you need to go to Steam and open the game properties for THE FINALS, then add this environment variable to the game's launch arguments :
If you already don't have any command line argument set for the game, you need to add %command% after the variable.

Once done, launch the game ! You should be able to see the difference immediately by looking at your character's clothing, they should look much sharper, details should be much easier to see.
To achieve a better result with the least amount of blur and ghosting, I recommend using FSR in Native AA mode
(Settings -> Video -> Resolution Scaling Method -> AMD FSR3 -> Native AA )

Finally, go to the practice range and test your results, you can press the HOME key to toggle vkBasalt.
And that's it! Have fun!

vkBasalt OFF
vkBasalt ON

You may ask : « What's vkBasalt »; And that's a good question!
vkBasalt is a post-processing layer for Linux, it works with VKD3D and DXVK (the translation layers that allows you to play DX12 & DX11 (and lower) games on Linux).
It might sound like Reshade, and even if the results are similar, it's not exactly identical :
vkBasalt relies on Vulkan (therefore it's not OpenGL compatible) to inject a Vulkan layer to the image through VK_LAYER_PATH, meaning that vkBasalt injects the required modifications into the Vulkan layer, and not into the game itself. This causes no issues whatsoever with Anticheats, there is no documented ban in any game to this day.
Unlike Reshade, vkBasalt uses native functions to modify the final image, and it doesn't require loading a DLL which hooks DirectX functions. Meaning that this will not change your game's configuration or file integrity.

vkBasalt doesn't increase latency or input lag. The performance impact is estimated to be between 1% and 2% depending on configurations.
My own tests indicate no noticeable difference, take these numbers with a grain of salt, as they might be overestimated. However please note that if you decide to add more effects to vkBasalt, the performance impact might become measurable even if it remains minimal. In any case, the performance impact is still lower than it would be with Reshade on Windows.