www.makemkv.com

Having been told of the existence of BDinfo as a way of identifying which titles I want to rip from a disc, I can't make it work, at least not under Catalina.

The most recent version of the app I can find is 1.2, and while it runs, the BDMV file on any Blu-ray I try is always greyed-out so I can't select it.

Is there some kind of trick to make it work? Or is there a better, alternative app for OSX?

I don't know if it's worth the effort but you could download a windows evaluation ISO from Microsoft and set up a virtual machine with Virtual Box on your Mac. You don't even need to activate it to make BDInfo work in it.