So I installed the beta version of Catalina just to see what it looks like and what is working and not working. The OS is nice. A lot of graphics have been updated, and it looks more "modern". A lot of things are the same, and some things have just been moved. As we've all been told before, the client side of Indigo runs perfectly on Catalina... I haven't run across anything that seemed "broken". I have not and will not try to install the server, as I know it won't work.
One issue I did run into was with the new Music App. I have the Apple Remote App on my iOS device, and am able to control iTunes in Mojave. But I can't use the Remote App to control Music in Catalina. There simply isn't the remote "button" to click on to enter the authorization code from the Remote App to link the iOS app and iTunes. And likewise, I can't link Indigo and the Music app for the same reasons. I'm going to report this to Apple, but not sure if they will fix it. So for those of use who use Indigo and iTunes, this is just one more thing to be aware of BEFORE you upgrade!
But this is beta... not going to worry about it 'til it's released.