The newest Grim Dawn update has done some interesting things. I no longer need to use the Grim Internals mod as a lot of the features I used it for are now baked into the game.

However, I still need my Rainbow Filter.

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Image Credit: SudoMistress

How to Install Rainbow Filter when on Linux

1. Go to Rainbow Filter
2. Download the file of your choice. For me it was [Files] Full Rainbow (English)
3. Extract contents to directory of choice. The directory will be called Grim Dawn. Inside it will be another directory called Settings and in that directory will be all kinds of things.
4. Open Steam
5. Right click on Grim Dawn -> Properties -> Installed Files -> Browse…
6. Move the Settings folder to the folder where the game is installed.
7. Profit