The Mandalorian episode likely comes later. The epilogue is seemingly set shortly after the defeat of the Empire in Return of the Jedi, which would put it around 5 ABY (ROTJ ending at 4 ABY). The Mandalorian was stated as starting five years after Return of the Jedi, which would mean about a four year gap.
Of course, this is not certain, and Dave Filoni has indicated that it's possible that the epilogue didn't start shortly after the Battle of Endor.
“Right. But no, it’s an interesting one… That’s not necessarily chronological. I think the thing that people will most not understand is they want to go in a linear fashion, but as I learned as a kid, nothing in Star Wars really works in a linear fashion. You do [Episodes] Four, Five and Six and then One, Two, and Three. So in the vein of that history, when you look at the epilogue of Rebels you don’t really know how much time has passed. So, it’s possible that the story I’m telling in The Mandalorian actually takes place prior to that. Possible. I’m saying it’s possible.”