I only know of the regular and Chromatic Sub-races of Dragonborn, tell me of these ones.
Dragonborn are separated into three sub species. Chromatic, Metallic, and Gem. They all get a 2d8 that scales really well with constitution and levels that can be used with multi attack as a replacement for one of the attacks. Uses scale with con modifier. They gain an additional ability. Chromatic gain immunity to their element for 10 min once a day, Metallic get a second breath weapon that either knock back or incapacitate for one turn(your choice), Gem get gem flight for one minute.
Gem Dragonborn are non elemental like radiant, necro, psychic, force, etc. So their resistance is kind of worse but the breath is way stronger.
A lot of feats, features, and spells too I think. They even have better kobold stuff. Due to the people that made them, its very very likely to be official content very soon.