I'm currently trying to bump the version of pydata-sphinx-theme that we're using (#27658), so we can get recent accessibility improvements from the theme. It's not currently possible to load the version switcher hosted at https://matplotlib.org/devdocs/_static/switcher.json on the documentation build that CircleCI generates. The console error is:

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://matplotlib.org/devdocs/_static/switcher.json?v3.8.1-1173-gfa55c9f44. (Reason: CORS header ‘Access-Control-Allow-Origin’ missing). Status code: 200.

Is there anyone who has access to the Matplotlib website that can fix this to allow pages served by https://output.circle-artifacts.com to load https://matplotlib.org/devdocs/_static/switcher.json ? If this needs any more debugging, here's a link to the full CircleCI doc build on the PR updating pydata-sphinx-theme.