how to ungroup windows on mac

I believe that you should try to adapt to a different workflow:

1. You could press ⌘+` to cycle all the windows of the same application.
   Note: this is not the apostrophe key, it's the backtick key.
   Non-shifted tilde ~ left of z on a UK keyboard, left of 1 on US.
2. Try App Exposé:
   • Trackpad
     System Preferences → Trackpad → More Gestures → App Exposé to configure your preferred gesture.
   • Keyboard
     Press F10

I understand this is not a precise answer to your question, but I believe that switching from Win/Linux to Mac OS, involves some adaptation.

I found that going to System Preferences -> Mission Control -> Then untick "Group windows by application"

Then using F3 shows all open windows. You still have to use the mouse to select, but I'd be surprised if that's not fast enough.

Also, leverage CMD + H for hiding applications you aren't using so when you press F3, there are fewer windows confusing your selection.