There are many older post about RT 5.7 not running on Catalina. No updates have been provided.
There is a closed issue on GitHub " macOS Catalina Crash — Incompatible Library #5385"
macOS Catalina Crash — Incompatible Library #5385
On the RT download page there is a link to a message:
macOS Build Issues
23 Sep 2019 (Monday) by DrSlony
We are aware that the current macOS build of RawTherapee 5.7 (sha256sum
70f7b7f) crashes when run on some versions of macOS. We are working on the problem.
If you experience this problem, downgrade to RawTherapee 5.6 until a new 5.7 build is ready.
This message was posted 5 months ago.
So, it appears that there will not be a fix? RT will no longer run under the current Mac OS?