It seems that Reason 11.1 works well on macOS Catalina.
But be careful if you are using Softube VST/Softube Central to authorize & download VST.
I bought Softube VSTs during the black friday, then I had to update Softube Central application and other software to be able to use/download the VST.
But the latests versions of Softube Central and VST are not compatible with Reason 11.1.
It works with others software such as Ableton, and I had to downgrade to Reason 11.0.1 to be able to use my softube plugin again ...Fatal error: 100000
A fatal wrapper bootstrap error happened. This software cannot be loaded. Please contact the software publisher for support using this software.
It could be better, if I could downgrade Softube Application & VST but I had no idea how to do because of authorization program and hard to find previous version of the Softube VSTs.
I am not sure the issue come from reasonstudio or softube side, but I guess, it's just because softube application are still not 100% compatible with Catalina.
So... just in case you are using softube services, with reason 11.1 I recommend you to not update anything (even if you buy new VST) just be patient before downloading.