For a very long time I had the macOS Mail app set up with a keyboard shortcut borrowed from Outlook: cmd+return. This worked forever and my muscle memory became very used to using it both on my Mac and my Windows work thing. The Keyboard control in System Settings accepts the shortcut, then completely ignores it. I've tried deleting it and starting over but that doesn't work either.
It stopped working in Tahoe and still does not work in GGate.