Compatibility Report

• Name of the game with compatibility issues: Shadowcrypt
• Steam AppID of the game: 316810

System Information

• GPU: RX 570
• Driver/LLVM version: Mesa 21.1.1 - kisak-mesa PPA
• Kernel version: 5.8.0-53
• Link to full system information report as Gist
• Proton version: 6.3-4

I confirm:

• [X] that I haven't found an existing compatibility report for this game.
• [X] that I have checked whether there are updates for my system available.

Symptoms

I'm not sure how to categorize this game, I don't know how this game performs on Windows. It might have similar issues.
The Steam Discussion section mentions some low fps issues, but I haven't seen high fps issues. However, with tweaks the game is playable from start to finish.

By default the game will run at approximately 130fps. While technically playable, for this game, a high framerate makes the game impractical to play (player movement and enemy movement is too fast).

The game offers a beta version (beta - version 1.33 branch). Again the game is technically playable, it also has a different framerate issue. But for the beta the framerate is locked at 30fps. This is the opposite issue (player movement and enemy movement is too slow).

Using libstrangle and the non-beta (default) version, the game can be played at 60fps and is playabe from start to finish.
strangle 60 %command%

However with Proton 6.3-4, the game will crash with libstrangle

Solution

Roll back to an earlier version of Proton. For me 4.11-13 worked with libstrangle.
Use the lauch option: strangle 60 %command%

The game will play at 60fps, which enables the game to be playable from start to finish.

Note - by default the game uses a CRT effect, which can be toggled by pressing 4.

The game lists achievements, but they are disabled. Supposedly they only work with the beta version, and I didn't find a solution to the low fps issue in the beta.