Thanks for the question. Yes, Catalina represents the final “end of the line” for Aperture, which is tragic (and stupid, frankly).
– Apple has finally added the ability for 3rd party apps to read the Photos library – this support was added in Catalina.
– RAW Power 3.0 will add this support, which means you can use it as a front end for a Photos library. The feature set will be *at least* what you have in RAW Power for iOS, plus ratings. I’ll provide more info when I know more.
– I don’t have a release date for RAW Power 3.0, but my goal is toward the end of the year. Catalina itself doesn’t ship until sometime in October.
– With this functionality, you can convert your Aperture library to Photos (using Photos). This preserves adjustments, metadata, etc. There are some exclusions and some conversions (e.g., ratings become keywords), but most data goes right over.
– When RAW Power 3 is out, you can use it as a front end instead of (or in addition to) Photos. So you get the benefits of both.
– I recommend NOT upgrading to Catalina until at least RAW Power 3.0 is out. There is no forced upgrade to Catalina, unless you buy a new Mac after Catalina ships, which will have Catalina pre-installed. Aperture will continue to work on pre-Catalina systems, so you can just leave a machine running an older OS if you like.
I hope this helps.