So, I tried an experiment last night; upgrading a second clone of my Mojave system to macOS Catalina just to see what would happen. I was VERY surprised by the results.
Out of nearly 800 Audio Units, only about 19 failed Logic authorization, and only about 6 actually couldn't run on the new OS and were uninstalled. Those 6 were free plugins I've picked up along the way that are way outdated at this point (side note: All of the plugins I own are on the latest versions, so nothing I'm reporting here is due to not having updated).
Some key things that failed Authorization: Antares Harmonizer 4.1, Guitar Rig 5 MFX, some UAD plugins, but this is because of the Apollo driver not being supported by Catalina. Most actually still managed to pass, however, but won't run without the DSP card obviously.
I expected the UAD drivers not to work since Universal Audio has a warning about this on their site. This point is a big deal for me, since I use an Apollo.
However, that was IT. Everything else passed authorization, and opened and ran, including some outdated or no longer supported plugins (like CamelCrusher, which I happen to use a lot, and an old version of Oxford Inflator).
As far as other DAWs, Pro Tools 2019.10 didn't open at all, and gave me an error message saying it's not supported for macOS 10.15. The message came from Pro Tools itself, not macOS, so I'm guessing Avid added it in the latest update. This came as no surprise to me, however. I was not expecting Pro Tools to work since Avid hasn't announced Catalina support. I do realize this is a huge dealbreaker for most people here, since there are mostly engineers here. It's slightly less of a dealbreaker for me since most of my time producing is spent in Logic.
I'm getting a 16" MacBook Pro soon, so the most vital thing I'm waiting for right now is the UAD driver for my Apollo. Pro Tools is a close second, since it's where I do most of my tracking. I produce in Logic, which is working great, with the overwhelming majority of my plugins showing up. I decided to conduct this experiment because of the 16" MBP, which I'd likely need to be on Catalina to use (unless it'd be possible to downgrade to Mojave, which I might try).
I didn't open Live 10 Suite since I don't use it much. But might test that out just for the hell of it.
Here's a list of software companies whose products I own that passed authorization in Logic and ran, aside from the specific exceptions I mentioned above. If anyone has questions about specific plugins, let me know and I can verify for you that they're working if I have them.
Accusonus, Antares, Arturia, Audio Assault, Audio Damage, BBE Sound, Camel Audio, Celemony, D16 Group, Dmitry Sches, Eventide, FabFilter, FutureAudioWorkshop, FXpansion, iZotope, keilwerth audio, KV331 Audio, LennarDigital, MOK, Native Instruments, Nicky Romero, NUGEN Audio, Overloud, Output, Plugin Alliance, Reveal Sound, Rob Papen, Sonic Academy, Sonnox, Soundtoys, Spectrasonics, Sugar Bytes, Synapse, Synchro Arts, TAL-Togu Audio Line, Valhalla DSP, Waves, Xfer Records, XLN Audio