Does xTuple support MacOS Catalina?

Yes, if you are running xTuple version 4.10.x or newer, MacOS 10.15 (a.k.a. Catalina) is supported. However, versions of xTuple prior to 4.10.x will not run on Catalina. The reason for this is that xTuple 4.10.x is the first Mac client series to be built using 64-bit architecture. Catalina requires applications to be 64-bit. Mac clients prior to 4.10.x were built with 32-bit architecture.