How to add Flatpak games to HGL?

[ShredderWalnut]

Hi there,

I'd like to add games that I downloaded from Flathub to HGL, e.g., Dungeon Crawl Stone Soup and Cataclysm: Dark Days Ahead. I have no idea which file to choose as the executable, or the correct command arguments, if any. I've tried my luck with numerous combinations but none worked.

Thank you in advance for helping a very frustrated player out!