Dragonborn technically existed in the 3E Forgotten Realms, although it was because of a not very well received or widely spread splatbook. Basically Bahamut changed volunteer humans who wanted to fight evil dragons in dragonborn. But those were few individuals.
The majority of dragonborn came from 4E lore when the world of FR merged with another world and a country of dragonborn was planeshifted over. On their world they were a slave race to true dragons. In 5E that place planeshifted back, but as dragonborn had by then also settled outside of that area several communities remained in the forgotten realms. In FR dragonborn were never directly related to dragons. Offspring of dragon/humanoid pairings are half-dragons (which were never really playable very well) and further down the line draconic blood serves as explanation for sorcerers.
Originally Posted by Eldath
I dislike gnomes because they represent the progress of technology in a world where I don't want any advanced technology.
Most stuff gnomes invent fit into the technology level of the FR. D&D in general is early renaissance and there specialists had a basic understanding of chemistry although often coupled with alchemy and there was also construction of clockwork, mainly in the Islamic part of the (real) world that had its golden era during that time.
