We have a plugin that implements the has_initial_backup_settings to display some settings in the course backup view. After our migration to Moodle 3.5, our plugin disappears from the 'initial settings' stage and has started to appear in other stages but it is being displayed wrong.
I have tracked the origin of this change to
MDL-31443 and MDL-60923. Both have modified the instanceof has_initial_backup_settings validation to instanceof backup_root_task and instanceof restore_root_task validations. The new validations clases are implementing the has_initial_backup_settings interface, so it will be possible to revert that part of the change and use the original validation, this way, our plugin would appear again in the rights stages and fixes on both core tickets should still be working.