It was time to bite the bullet and upgrade this site to Drupal 10, which went pretty smoothly, but of course, never start this sort of process without a backup.

Drupal has made huge advances with upgradability since Drupal 7. Going from Drupal 8 to Drupal 9 and now to Drupal 10 has been a progressively smoother process.

In the case of this site, it was simply updating composer.json and changing some lines in composer.json like this:

Before: