Linux Version Zoom microphone TEST REPLAY does NOT work.

[stonevl]

I'm running Zoom on Linux (Ubuntu 20.04.4 LTS) on an older Dell-XPS-L322X machine. When I try to use the Mic test, I can SEE that the volume indicator in the Test Window indicating the rise and fall of the sound.  However, i never HEAR the playback of my "testing 1-2-3" although if I continue on and connect with another user, sound and video both work. 

I suspect this is either a programming error in Zoom or the Ubuntu audio driver, but I can't solve in nor have I found others with same problem.  (Yes, I've removed and reinstalled both the OS and Zoom.)