I am using latest Mac OS 13.4 and JetBrains Fleet 1.19.95. Maybe it's just me, but delete button don't works for me with any of the keymaps available – I receive just beeping.
I tried editing default keymaps, but receive only beeping or wrong behaviour: backwards deleting when I don't expect it, etc.
UPD: I made some additional investigation and deleting left is called delete backward, but to delete selected text I need to use delete forward. Also, for some reason on Mac OS there is delete button shortcut that is directed right, I don't even know which button is it! Plain delete button gives delete directed to the left. Maybe someone has keymap for Fleet working appropriately on Mac OS and can share it?