Same here, my girlfriend is on the Catalina Beta program and has this issue. Not a solution but I've noticed that if you resize the window it actually shows the content (but if you click anything, you will need to re-resize to show the updated content).
Not the right place, but there is a graphical glitch on the iPad OS beta as well: where the cloud icon is on the top left of the screen, there is some "white" covering the area. Still, the app works and is fully usable.