If it's true then Longstaff needs to think very carefully on it, because he has a fantastic chance of cementing down a regular first team spot for us which could net him very very good wages and family security for life.
If he goes to Man Utd he could end up as mere slim pickings as far as first team goes, for a good few years which could actually break him as a top player but also wreck his chances of ever making it into the bigger time earning league, as well as the obvious potential of an England career.

In my view, as it stands, Newcastle offer him the best options.