The syntax you are suggesting looks great to me!
I don’t think we’d need to rely on hover and agree it is noisy. Maybe headings can simply become links to themselves that can be selected via long press or ctrl/right click? Only issue there would be headings where people create links as in eg below, but not sure this would matter for the vast majority of cases.
# [this is a heading](https://someurl.com)
I still like @mcwumbly’s suggestion from back in the day: