All reports of menu-item-contains-unknown-tag for the archive. The extended description of this tag is:
The menu item has a line that has a tag in it that is not one of the standard tags (needs=, section=, title=, longtitle=, command=, etc). While other tags can be used for specialized purposes, this is rare and it's more likely the tag's name is misspelled.
This tag has not been emitted in any package tested by Lintian.