MacBook Pro M1 external display connection issue
Numerous people report issues with ultra wide screens (width &gt; 2*height) and M1 Macs. By my count, there have been three questions here in the past week.  There are 12 pages in this macrumors thread.
I suggest a web search for &quot;Mac m1 ultrawide&quot; to get a feel for the number of problems.
Apple have acknowledged the issue, but are yet to provide a fix. For a report on this 9to5Mac.
To reduce the number of uncertainties, try and get the monitor to work without any dock.  When that fails, contact Apple.
I am aware that this &quot;answer&quot; does nothing to resolve problems with utrawides, it is little more than a pointer to it being a widespread issue.