"My issue is getting good sound quality from the 'Net using Zoom and Jitsi."
This is probably the best & most useful piece of information you've to work with. That seems to point away from a audio card, audio software/drivers, cables, etc. I don't use either of these apps, so I could only suggest to see if there these apps have some tests you can do or settings to adjust or do a web search on "Zoom voice quality problems." Seems silly, but I'd try testing with a few different browsers. There could be a problem with voice being processed between these apps and your browser. The other thing you could do is maybe find some internet audio quality test site or maybe make some test calls over google voice, skype or similar web voip app.
