Big Sur Upgrade and what worked for me
 

The following troubleshooting step worked for me, with Mac OS Big Sur.

No matter how many times I reinstalled the DisplayLink Manager or confirmed that it was enabled under Screen Recording, I had to REMOVE it from Screen Recording the launch the DisplayLink Manager in the Applications folder for it to finally work correctly. It then shows up again in the Screen Recording section and once enabled works well.

Hope this is able to help someone else, it was really frustrating.

Cheers.

Lucky
 

I'm not such lucky.
I've Tried everything. Also, removing ( - ) the displayport from recording screen section.
Reboot, ungplug, plug, add recording screen again. Uninstall, install.
No luck.

Even one dongle screen is attached and working. Second one is completed black. And the Displayport menu shows "No Monitor Detected".
(Macbookair M1)

Still looking for a resolution

Specs
 

You do not list all the hardware and software involved. In particular what Hub or adapters you are using. The displaylink software only works with dispaylink based chipsets found in many hubs. Straight thunderbolt docs will not work.