theming – 9 – How customize 403 page for some routes?

On a D9 site, with an existing custom 403 page twig. I’ve been requested to show a different, variable, message from the “standard one” for a couple of specific routes.

I’ve tried with theme_preprocess_page__403(&$variables) but I couldn’t determine the original route.

E.g. using Drupal::routeMatch()->getRouteName() I got system.403 instead of the route name I need to check. I’ve checked solutions to find the refer route but none of them seemed to work.

Actually the two routes that need this specific 403 are created programmatically with a *routing.yml and relative controller in a custom module.

I wonder if it is possible somehow to specify the redirect path if the route requirements fails. I didn’t find any documentation about, but that would another way to implements this requirement.