How did Mando know where to find Grogu?

Referring to the Book of Boba Fett. Mando leaves Tatooine to gift Grogu with the beskar armor, and seems to already know exactly where he is.

How did he know? Was Grogu's location (and by default the planet where Luke was starting his Jedi academy) common knowledge, or??

Hasn't been told in canon yet. I've just head-canoned it as Din and Luke exchanging contact info off-screen. Maybe Luke commed Mando the coordinates from Red 5 as he was flying away.

Luke telling Mando where he was taking Grogu wouldn't make sense. I doubt Luke ever intended for Mando to have visitation rights.

Perhaps Mando still has Grogu's tracking fob?