Displaylink not working after upgrade Catalina 10.15.4

[apb]

After upgrading to Catalina 10.15.4 (from 10.15.3) my DisplayLink monitor stopped working on my MacMini.

I read stuff here. I checked that the extension was still installed. I checked that it had permission to read the display. I rebooted. I uninstalled the Beta-version driver and reverted to the Release-version driver. I checked everything again. DisplayLink monitor remained blank.

Same monitor, same software on my MacBook: works fine.

Then I followed the directions here to report an issue. Downloaded the report tool, and ran it. Then I realized that the DisplayLink monitor was still plugged into my MacBook, so I reconnected it to the mini. It worked.

Thats right — the only thing that worked was running the reporting tool (while the DisplayLink monitor was not connected). Maybe it kicked the USB bus somehow? Very strange.