The entry for draconians in Fizban’s Treasury of dragons indicates that they are not Dragonborn. I think that was an idea that was dropped once actual draconians were added to the game.
I consider Fizbans "canon", albeit not Core. Canon enough for the Draconian.
Heh, I have the book and can get it if I have to, but am being lazy.
Judging by a quick search that finds a paraphrase, is the following correct in 5e Fizbans? The Draconian originates from shapeshifting a Metallic Dragon egg. The purpose is for an army of Evil, but they turn out to have free will and some choose Good. The Draconian species preexists the Dragonborn species by a "number of years". The Draconians explode when they die, dealing the breathweapon damage type. Some have wings.
If the above is true, can the following apply?
The same dragon magic that produced the Draconian also produced the Dragonborn. According to the playtest (UA3), the 2024 Dragonborn originates from shapeshifting the eggs from both Metallic and Chromatic dragons. Thus the Draconian is a "proto-Dragonborn" and is a kind of Dragonborn, relating to the Dragonborn in the Players Handbook.
Some Draconians have wings. But this is mostly irrelevant since most dont, and some with them are still incapable of flight. The ones who can truly fly might attain the ability at higher tiers. It is no problem if some Dragonborn retain a draconic tail or vestigial wings.
Draconians explode at death. Even this might be a cultural dragon magic custom, that a background can grant. (I want Dwarves that can petrify into stone at death, but this doesnt really affect any Dwarf stats.)
It seems feasible to use Dragonborn stats for a Draconian character, who is a variant Metallic ancestry.