Menu item extras template suggestions are only enabled for menus with custom fields.
The current behavior is that a menu link content entity must have a custom field for menu item extras templates and suggestions to be applicable.
@see \Drupal\menu_item_extras\Utility\Utility::checkBundleHasExtraFieldsThanEntity
@see \menu_item_extras_preprocess_block()
@see \menu_item_extras_preprocess_menu()
@see \menu_item_extras_theme_suggestions_menu()
OPTION 1:
Check if a menu has display modes and allow menu item extras templates and suggestions to be applicable.
OPTION 2:
Check if a menu is not locked (aka not an admin or devel menu) and allow menu item extras templates and suggestions to be applicable.
OPTION 3:
Leave the AS-IS and require a field to be added to allow menu item extras templates and suggestions to be applicable.
N/A
Possibly adding new utilities including Utility::checkBundleHasExtraViewModes
N/A
Active
3.0
Code
This. Just spent several hours debugging why the template wouldn't kick in. Added a field and voila.
Enabling layout builder, with custom layout per item works without adding other fields (because custom layout is a field).