Calling ObjC via your language of choice is like the easiest thing possible, solved multiple times over. Signing and notarizing outside of Xcode is also a solved problem.

IME people bitch about this but when push comes to shove just don’t want to do the required work, typically on flimsy grounds. It’s just not that hard.

The increase in Swift-only frameworks will eventually be a problem but it’s typically not a blocker right now.