With every client-side routing framework or library I know of, the trivial happy path will involve using their provided link component which performs client-side navigations on click but also renders an underlying anchor tag with href (and works with cmd-click, middle-click etc.).

You really have to go out of your way to break this, and I don't think client-side routers deserve any blame for this. Anyone who is ignorant or careless enough to ship broken links using a client-side router would be just as likely to break anchor tags with their own hand-rolled JavaScript.