If you are looking to replace the 32-bit-only Aperture with something else for photo editing on Catalina and don’t like Adobe’s subscription model, you may want to consider Capture One. It is actively supported, has the “buy and own” option, and is very capable though its interface may take some getting used to and/or customizing.

I tried the demo earlier this year and liked it a lot, and they even happened to have a promotional discount at the time, but for whatever reason the purchase button was broken for me. I’m sure it was either just my machine, or Phase One has fixed the bug long ago.