UnknownUnknown
A patch and ini edit are needed to get the game running in widescreen and in resolutions higher than 1440x900. A guide for this can be found on the page for Bolt on PCGamingWiki. You can ignore steps 5-9 of their guide, as the hex values don't exist in the .exe; it worked fine for me without doing this.
While it's seemingly not specific to Linux/Proton, there's a bug in the mission Hide and Sneak which makes the mission impossible to complete without restarting the level again. A post about this can be found on the Steam Community pages, titled "Game is Ducked". You may have to restart the game if this happens, as quitting to the main menu and loading my save got the game stuck in a pause menu loop.
The game wasn't holding my attention so after the Hide and Sneak bug I stopped playing. For a kids game the difficulty curve ramps up fast. I can only assume this becomes Souls-like as the game progresses.
