Deleting unused files in Drupal 9
- removing unused orphan files from the file system modern Drupal 8 9 10
- drupal 8 remove orphan files
As of Drupal 8.4, files that have no remaining usages are no longer deleted by default.
You can change this in a configuration-file-only setting.
https://www.drupal.org/project/file_delete
files are still there for each revision, so to remove from being listed:
https://www.drupal.org/project/node_revision_delete
And finally (as Clay noted) https://www.drupal.org/project/auditfiles
And Unmanaged / Unused Files | Manage | Delete | Drupal.org
And Fancy File Delete | Drupal.org
Some of the solutions should be posted here: