There is a medium-sized website based on Drupal 9 that needs to be upgraded to Drupal 10. Here is a guide on how we upgrade this website.
Drupal 9
By Gast (nicht überprüft), 24 Januar, 2023
Problem
By Gast (nicht überprüft), 14 Juni, 2020
TypeError: Argument 2 passed to Symfony\Component\Routing\RouteCollection::add() must be an instance of Route, boolean given, called in RouteProvider.php on line 382
Drupal Update / Upgrade Error: