Unfortunately as far as I know the only way to pull standard (.wav) files out of an Audacity project is to bounce them down in Audacityâ€”there's apparently no way to put them together from the .au pieces. That leaves you with a short list of options..
- First off, in the discussion of a Terminal workaround (see below) they seem to imply that Audacity should open and run under Catalina, but you won't be able to record into itâ€”if all you need to do is open it and bounce down tracks to .wav files, that may be worth a try before anything else (unless you've already tried it and it didn't work)..
- Borrow a Mac with an older OS to render .wav files in Audacity to use in GB
- If possible, create a partition and install Mojave on it so you can open Audacity
and export proper .wav files
- Try the Terminal workaround described on the Audacity Forum
- Try Audacity 2.4 Alpha, a pre-release version that is supposed to include Catalina compatibility
(though it's not clear if that's in place yet)
Re the last two optionsâ€”be VERY cautious with Terminal workarounds, and be even more cautious with alpha (early pre-release) software, which is liable to be very unstable on your system. I DO NOT RECOMMEND either of these two optionsâ€”I'm just letting you know that they exist.
That said, if you're an experienced hand at macOS and want to try the Terminal trick (keeping in mind it reportedly does not work for everyone), or if you're willing to try out possibly unstable pre-release software, then here are links to the Audacity pages that reference those options (again, I'M NOT RECOMMENDING EITHER of these!)..