Edit: the disappearing contents of the A tag were due to an issue with custom styling, however the empty A tag is still a problem for screen readers. The RTD team has fixed it on their version by using aria-label instead of alt for the tag, so I think making the same change would fix this issue.

When we updated to mkdocs 1.3, our accessibility tests started failing on all pages. It turns out the top-level "Docs" breadcrumb has disappeared in the default theme.

Before:

After:

It looks like the A tag inside wy-breadcrumbs was changed so that it no longer has any content, which is invalid HTML for a link, hence why our accessibility tests failed.