I was watching the episode again and I noticed something, Giddeon seems to refers to Dyn as a "decommisioned Mandalorian" and it got me thinking.
We know that at the end of Rebels (just before R1 and ANH) the Mandalorian people tried to rise up and free themselves from the Empire, but it seems highly likely that the Empire came down on them hard and the attempt was unsuccessful. The use of the term "decommissioned" makes me wonder if the Empire's solution for dealing with the Mandalorians was to force a complete disarmament. Ban the wearing of Mandalorian armour, take their supplies of Beskar, stop them from ever being able to rise up against the Empire again.
That would mean that the Mandalorians we see in the series are those who refused to disarm, who fled and hid rather than give up their traditions. From what we have seen of the Mandalorians in the series they do seem to be hardcore traditionals who would not have been willing to give up their beliefs and traditions under any circumstance.
It would be interesting if by the end of season 2 Dyn has gotten hold of the Darksaber as we might see more about what has happened the Mandalore, and see the effects of someone appearing with the Darksaber.