Do I need SharePoint Global Admin to Promote a Sub Site to Site with the ShareGate Tool?
First of all see my ADVERTISING section relative to add’s, publicity in this Site. I use others Products or Tools also, I’ll talk about them when makes sense for an article.
You have an option only to promote Sub Sites to Sites in the UI as a feature, but do I need SharePoint Global Admin rights to use it? YES, this is an exception you must be aware of. You don’t want to start brainstorming with stakeholders without this information, because not in all migrations the Governance give you this option.
Remember, a migration is to be FLAT, don’t break the Service Rules and flexibility.
Note, see this article about the FLAT APPROACH