Mon Mothma (Genevieve O'Reilly)
First appearing in Return of the Jedi, Mon Mothma was a Republic senator who broke away to become the leader of the Rebel Alliance. Genevieve O'Reilly played a younger version in a deleted scene in Revenge of the Sith. O'Reilly then took on the role in Andor, showing how Mothma began her planning to take on the Empire.
Ahsoka has Mothma now Chancellor of the New Republic, still trying to make it work and not happy to learn of Thrawn. It appears she'll be giving Ahsoka her mission to take Thrawn down.
Huyang (David Tennant)
He may look like a standard droid, but Huyang is actually thousands of years old. He has been the master craftsman of lightsabers, teaching a hundred generations of Jedi how to make them. Somehow surviving the fall of the Order, it looks like Huyang is back and no doubt aiding Ahsoka in hopes of getting more Jedi to use his works.