Clamshell mode not working is reported in the release notes for Displaylink manager v1.2
For me it works though. What I suggest you try:
- remove all current displaylink software through the dedicated uninstall application :
- Reboot (don't skip this)
- Download & install the
older version and follow instructions during the installation.
- CMD + Space > type "security & privacy" hit enter, check under "General" tab if it asks you to "Allow" displaylink manager, and after that the privacy tab on screen recording.
Last and most important step:
Reboot
If this wouldn't work you can also repeat the above steps (with reboots) and try this
legacy driver. I can confirm both versions work fine (not best though since not "latest").
I have a MBP 2020 (10th gen) with Dell D6000 and 3 x 24" monitors working for years now. Also on Bigsur 11.1 with DM 1.2