Apple has deprecated a lot of things and seems to be trying to move everything over to AudioServerPlugins, which essentially requires a full rewrite of the drivers. The architecture isn't similar at all (AudioServerPlugins actually follow a Microsoft-style COM interface, among other things). I don't even think Apple makes any sample code for updating old Firewire drivers to run on Catalina, so it's a tough slog, and low-level CoreAudio expertise to update old drivers is getting scarce. Traffic on the CoreAudio developer mailing list is down to less than a dozen posts most months. There hasn't been a single post to the mailing list yet in October.
I strongly suspect that some interface vendors are not going to update their 32 bit drivers for Catalina. (MOTU in particular is one, which kind of marks the end of an era because they used to be champions of some of the best CoreAudio features, like Firewire clock syncing.)