Putting aside the fact that the Gods may choose whoever they want to be Dragonborn for mysterious reasons...

Some info from UESP that may be relevant to this discussion:

Bretons are have both Man and Mer lineage. They are the result of interbreeding between the Aldmer (especially Direnni Altmer in High Rock) and Nedes (it is disputed whether the Nedes are early Nord immigrants from Atmora or whether they were an indiginous people of Tamriel).

Bretons also trace back lineage to Atmoran (Nordic) slaves taken from Skyrim, who intermingled with Altmer.

On a different note, is there anyone who thinks these discussions are irrelevant since all Men and Mer (and I assume beast races?) come from Ehlnofey?

confused on what your asking here if its can a breton be dragonborne then yes

he talking lore naow. He knuwz all races are playable. But he is talking about lore.