If you take a screenshot, open the screenshot via clicking it in chat, drag and drop the screenshot from your image viewer to some other program (e.g. Discord, Reddit, etc. doesn't matter) then close the image viewer, it crashes the game.

This seems to be a Linux-only issue as far as I'm aware. Sometimes it doesn't crash when you follow these steps. It might have to do with the fact that the game seems to freeze when viewing the screenshot.