Hi all.

So I may have fixed this for my end, and hopefully others may be able to use the same fix.

After a tip from Karl Auerbach and this link:

    https://developer.apple.com/forums/thread/97805

... I was able to fix the problem by disabling Bluetooth.

However, disabling Bluetooth was not enough. I also had to disable all Location Services.

After that, I re-enabled Location Services and only allowed for two features:

    - NetSpot
    - Find My Mac

With just those two location services, as well as Bluetooth disabled, I have no more high jitter.

App performance like Zoom and Youtube uploads are now crisp, with 0.0% packet loss.

So looks like that Bluetooth is a huge problem. Confirmed by opening the "Console" app, and adding "scan" in the filter bar, top right.

A peak latency of 13.5ms after 300 packets:

Marks-MacBook-Pro.local (172.16.0.239)                                                                                                                                                                                       2020-10-30T21:06:05+0200
Keys:  Help   Display mode   Restart statistics   Order of fields   quit
                                                                                                                                                                                                             Packets               Pings
 Host                                                                                                                                                                                                      Loss%   Snt   Last   Avg  Best  Wrst StDev
 1. 172.16.0.254                                                                                                                                                                                            0.0%   300    3.1   4.8   2.2  13.5   1.9

Mark.