Just now I downloaded “audacity-macOS-3.4.1-universal.dmg”, mounted it, and dragged the app to the Applications folder on my Mac under MacOS 10.14.6. Double-clicking, the first launch hangs on “Verifying ‘Audacity.app’…”, about halfway through.
I’m hoping that the new version, once it works, addresses the problem in opening AAC files even though ffmpeg is successfully installed.
And when I go there, sure enough, there is the Universal Binary.
And full stop. There are no other instructions and no other suggestions how to find more.