Call Apple to report this issue so they are aware of the problem. Even if they can't offer a solution right away, at least they have a record of you having trouble and can incrememnt the record they have of the number of people experiencing this problem.
How to Force RGB Color Output instead of YPbPr on your M1 Apple Silicon Mac for an External Monitor.
This step-by-step video tutorial will guide you through the procedure of forcing RGB color output on your M1 Mac.
