Which Rosary Mysteries on Advent Sundays?

There is no formal Church decree on this matter, although, because Sunday is always the Lord’s Day, the Glorious Mysteries are arguably the most appropriate.

Similarly, one can argue that, apart from Sundays, the Joyful Mysteries are most fitting during the Christmas Octave, the Sorrowful Mystery during Holy Week (except for the Luminous Mysteries on Holy Thursday, given the institution of the Eucharist that day), and the Glorious Mysteries during the Easter Octave, including Easter Friday, since it too is a solemnity.