Base theme stable9 has not been installed.

I can confirm this happened to me when I updated to the latest version.

I found a solution at https://www.drupal.org/project/bulma/issues/3361624#comment-15075814 🐛 The base theme stable9 is not enabled when updating the theme on Drupal 9.x Active . Basically, stable9 needs to be enabled, but it is a hidden theme.

drush theme:enable stable9

Will enable the theme. You should also manually update your core.extension.yml file.

stable: 0 to
stable9: 0

Maybe something that could be added to the release notes? https://www.drupal.org/project/zurb_foundation/releases/9.0.0-beta2 →

Thanks!

hmmm.... it looks like zurb_foundation's composer.json still is requiring drupal/stable. I'm not sure if this should be addressed in https://www.drupal.org/project/zurb_foundation/issues/3355260 🐛 The base theme stable is not operated correctly Fixed or a new issue?

I created a MR on https://www.drupal.org/project/zurb_foundation/issues/3355260#comment-15... 🐛 The base theme stable is not operated correctly Fixed since I thought that would be best. Hopefully all goes well.

drush theme:enable stable9

is the quickfix indeed.