The build workflow issues the warning
The github-pages gem can't satisfy your Gemfile's dependencies. If you want to use a different Jekyll version or need additional dependencies, consider building Jekyll site with GitHub Actions: https://jekyllrb.com/docs/continuous-integration/github-actions/
See https://github.com/MDAnalysis/MDAnalysis.github.io/actions/runs/18808516795
Perhaps this is related to the fact that pages are currently (2025-10-26) are not being deployed??