Microsoft doesn't allow Admins to disable "Public" Teams!

Public Teams mean there's no approval for joining a Team, this means anyone could get access to confidential conversations and documents.

To remediate this I went full on workflow:

A PowerShell Azure Runbook runs once a day and finds any Public Teams. It then changes it to private and adds these Teams to a SharePoint List

A PowerAutomate (Flow) is triggered when an item is adding to the SharePoint List.  The Flow emails the Owner of the team explaining what has been done and why, it also emails IT Security informing them of the Team and Owner.

Quite proud of that one :)