Interesting question. On steam there is a red box simply saying "This product is not compatible with macOS 10.15 Catalina.", so the devs are aware of this issue but most likely don't have an ETA when they will update. The problem is that Shadow Tactics is based on Unity 5.4.4 (released in January 2017), which is 32bit only on macOS, while on windows it already has a 64bit version. I also checked 2 unity based applications i have here from university projects: the one built with Unity 2017.2 (released in October 2017) is 32bit, the one built with Unity 2018.2 (released in July 2018) is 64bit, so I guess that Unity moved to 64bit on macOS with 2018.1 (released in May 2018). So getting Shadow Tactics running on Catalina, either requires to bring the currently used Unity version to 64bit (which would most likely require more than just recompiling the code, because in that case Unity would have moved to 64bit earlier), or updating to a unity-version that is 64bit (which would most likely require a lot of work because there have been changes to the engine so most likely some things will no longer work.