I just purchased BIAB 2020 mac yesterday and have the exact same issue. Unfortunately for me NONE of the solutions worked.

Things I tried in addition to the items outlined in this thread --
1.Looked on 2 additional mac computers for the sf2 files. Could not be found on any of the machines, or user accounts -- non even on a machine running Mojave
2.Re-download all sound libraries using logic/garageband
3.Download public SF2 files and added to the DLSMusicDevice

I can confirm i can use the DLSMusicDevice in Logic with the publically downloaded sf2 files -- however its not detected in BIAB

In response to the above, I only see the following on my machine:

AppleScript.component
AudioCodecs.component
AudioDSP.component
AUSpeechSynthesis.component
CoreAudio.component
JavaScript.component