I have tried all these options and can't get macbook pro, running 11.6.1 to recognise an external display since update to Big Sur. I note from forums that Monterey has the same issue. Is there a workaround?

Hello there, marguerite92!

Thanks for reaching out to the Apple Support Communities! It sounds like you have an issue connecting your external display to your MacBook. If you have followed the steps in the article If your external display isn't detected or appears blurry on your Mac and still have an issue, we would recommend reaching out to Apple directly by checking out this link to Get Support and they will be more than happy to proceed with additional steps.

Have a super day!