I agree that both Matthew and Mark mention Galilee. But is there something in Matthew that says that the discourse in chapter 28 takes place just before Jesus ascends?
The version of those meeting Jesus, Him directing them to tell the Disciples where to meet, then it goes into Jesus Commanding the Disciples, leads to the thought of being the same event. Then Mark claims Jesus' Ascends. However, Matthews does close on AMEN, which would make one believe Jesus does Ascend there because essentially the next event is the UPPER ROOM in the Book of Acts.