I have a MacBook Pro 13 with Catalina v 10.15.6. This is an Ableton system. Considering moving away from Mac and Ableton.
Push2 works, software instruments work. I have an Apollo twin - does not work. Also a Boss GP-10 - does not work. I am hooking them up individually without JACK.
Catalina introduced a change where applications have to get permissions to access the ‘microphone’ which is pretty much any audio input. Older versions of Ardour weren’t set up for this well (Developed before Catalina), but newer versions should work provided you give them permission.