The ubuntu charm is maintained by the Charm Collection (Charm Tech) team, but when maintenance was handed over, it didn’t come with access to a Charmhub account. It’s currently published by a meaningless ‘charmers’ name with an associated email address of juju@lists.ubuntu.com, which, from what I can tell, goes nowhere.
I have talked to current and past members of the Juju development team, and none of them have access to the Charmhub account, or the mailing list, and none know who might do. No-one answers the mailing list (most likely because there are no recipients), but mail doesn’t bounce.
Please transfer the charm to the charm-collection publisher.
If you need authorisation for this, please ask Jon Seager or @sinanawad.