This is a disappointment from Izotope. As a BiaB Mac beta tester I see this as odd. PG Music worked hard to avoid issues with the new OS and is ready. What's up Izotope? Isotope and Catalina

That’s especially odd since they just did a major release of Ozone 9. I bought the upgrade (for Windows) and the installer offers a download for Windows and Mac.

I own Mac and PC. I have been warned about some of my other music apps for Mac not to upgrade to Catalina till they get there stuff in order. Onsong app just informed me it is now ok to upgrade. It has to do with some new security features Mac is introducing in their OS is what I have heard. It is similar to Windows having signed drivers from manufactures that are compliant is what I am guessing.
Brian

macOS Catalina, the next Mac release, dramatically tightens security and removes 32-bit compatibility. That will cause incompatibilities with music software, requiring updates. Here’s what you need to know

Catalina compatibility checklist
macOS Catalina (10.15) is expected to ship in October, replacing Mojave (10.14).
What’s impacted:
DAWs and other software using plug-ins: Requires updates to work.
Drivers: Installation and operation requires update to work.
32-bit software, software that accesses 32-bit libraries: Incompatible. Cannot be used past macOS Mojave.
Software using legacy video libraries: Incompatible. Cannot be used past macOS Mojave.
Plug-ins: May require update for full compatibility – but may run inside updated DAWs, and will install if the user overrides OS’ installer requirements.
Hardware: If a driver is required for operation, you’ll need an updated driver and installer. Driverless (class-compliant) audio and MIDI gear is unaffected.

This is the whole report of what is happening with the Catalina upgrade CDM Report

I would suspect most software company's will have their updates very soon so just hang in there, no worries! Besides Catalina has not been released as of this post, though it will be sometime this month.