I have U3821DW (Firmware M2B101) which is on the supported devices list for the DDM for macOS. So I installed this (just released) DDM (Dell Display Manager) macOS. 1.50.0.0039, A00) on both my M1 Mac's. The M1 Mac's are supported and both Mac's are up to date, running the latest macOS Big Sur (v 11.6.)

1. M1 Mac Mini - Connected via (Original) HDMI1 + USB-B upstream cable 
2. M1 MacBook Air - Connected via (Original) USB-C cable

When I start the App I get a pop-up message (please connect a supported monitor) with a notification message about USB-C or USB-B or DDC/CI or firmware:

But all requirements are satisfied, and I can't find any firmware update for the U3821DW anyway!? 

- DDC/CI = on
- Using Original cables
- Cables inserted properly
- No Docking in between
- Bot systems restarted

I also read the Dell Display Manager on Mac User's Guide, but everything seems to be fine and it should working, but it is not!?