I will try out Fidel this weekend. Here is the way I got this to work:

- Make sure the executable bit is set on this Apps main binary

chmod +x /Applications/Fidel.app/Contents/MacOS/Fidel

=> With this change it launches normally for me and fullscreen mode works

- Use Enjoyable to map controller inputs to keyboard inputs

https://yukkurigames.com/enjoyable/ or

brew cask install enjoyable

What issue were you having before doing this fix?

@1nvalid without the executable bit set, the game fails to start entirely on Catalina.

AFAIK there is no controller support in the game itself on Mac OS. This is a shame, because it plays very well so far with a controller.