I thought that might be the case.
Some new information has come through from the developers.
Apparently, in addition to dropping support for 32-bit application, Apple decided to only allow software that they say you can run.
Beginning in macOS 10.15, notarization is required by default for all software.
This means that software developers have to ask Apple’s permission to allow their software to run on Catalina.
Apple have since relaxed this requirement - probably because it broke too much software, but the extent to which it has been “relaxed” is currently unknown, and may change with each macOS update.
Sadly, this decision by Apple goes against the spirit of open source software (What is Free Software? - GNU Project - Free Software Foundation)
“Free software” means software that respects users’ freedom and community. Roughly, it means that > the users have the freedom to run, copy, distribute, study, change and improve the software> . Thus, “free software” is a matter of liberty, not price. To understand the concept, you should think of “free” as in “free speech,” not as in “free beer”.
The new restriction probably violates the terms of GPLv3 (the current version of the GPL open source license agreement), so I expect that many open source applications will no longer be available for Mac users.
In the case of Audacity, the software license is GPLv2. At this stage I am unsure if Apple’s notarization requirement legally conflicts with GPLv2, though it is certainly against the spirit of GPL.
Given the above, I am surprised that Audacity runs at all on Catalina - perhaps that’s due to the requirement being temporarily “relaxed”. My guess at this stage is that although Catalina currently allows Audacity to run, it prevents it from accessing external resources, including audio capture (recording).
These problems are not unique to Audacity. Many other audio products are saying “don’t update to Catalina yet”, including:
Ableton
Acustica Audio
Akai Professional
Antares
Boss
Denon DJ
iZotope
Korg
Native Instruments
Numark
Pioneer DJ
Pro Tools
Roland
ROLI
Steinberg
and many more…
I note that many of these make USB hardware, so perhaps that’s an indication of problems with USB audio devices (?).
For now, the Audacity website says that Catalina is not supported by Audacity. That information will be updated when we know more.