Good luck with that! If you manage to get a working solution, I’m in the exact same boat as you and would love to see a fix.
I ran into the same issue a week ago, but I dug around a bit to find the root of the problem. The reason the sound visualization plugin cannot be packaged is because it has a dependent module, Kiss_FFT, that Epic apparently excludes during the build process of the UE’s launcher version.
Downloading and compiling the full source code did indeed provide access to the Kiss_FFT library (it’s in there, sure enough…), but I was still unable to package it thanks to “Kiss_FFT Module cannot be found” errors.
While not very helpful right now, I’ve been assured that a fix for this issue will be included in the next release.