So, it turns out we now need to start sending our apps to Apple for "notarization" if we want them to continue to run on macOS:

Note that in an upcoming release of macOS, Gatekeeper will require Developer ID signed software to be notarized by Apple.

This seems like really bad news for macOS, but given the questionable decisions Apple has made in the name of "security", for example secure kernel extensions, this is not unexpected. This basically implies that Apple is planning on acting as gatekeeper for any software to run on macOS, making it as restrictive as iOS.