Drupal 12.0.0-beta1: I read the removal list so you don't have to

Drupal 12 is mostly 11.5 with the deprecations deleted — and the deletions include nine modules a lot of sites run (Search, Contact, Toolbar, Shortcut...). The upgrade is a Composer-require checklist, Contact is the one to check carefully, and the Dec 9 Drupal 10 EOL makes it a deadline for some.