Using Drupal 10.0.9, menu suggestions per region do not work.
In the menu alter hook, the region is determined by `$variables['attributes']['region']`. However, this seems to be always empty.
1. Place the Primary Menu block in the Header region
2. Add `menu--main--header.html.twig` to your theme
3. Clear cache
4. Notice that the template is not recognized
Active
2.0
Code