@greatmatter: I encountered to problem with the superfish library not being found when I used the Drupal administration interface to update the superfish module from 8.1.6 to 8.1.7 in Drupal 9.5.11. The library directory was still called superfish. I then used Composer to require superfish ^8.1.7, and the superfish library directory was deleted and properly replaced with drupal-superfish, as you surmised. All is working now.
I did not initially observe any of the errors noted above. The very obvious symptom was that all of my menus and submenus were expanded, and much of the basic CSS styling was missing. I was really sweating until I found this thread. Thanks to all!