jmartkdr2
Hero
There was a supplement that had "racial paragon classes" so you could 3 levels of elf (gaining proficiency with traditional elven weapons, a little bit of magic, some bonuses to elven senses, etc.) They were available for all the PHB races and maybe some others, and I think the biggest one had 5 levels.I remember back in earlier editions, your character's Race was also their character classes...you could play a 5th level Dwarf, for example, and you would gain additional/improved Dwarf features as you gained levels. I know it was standard for non-human races in BECM and B/X, but I could have sworn I saw options for it as recently as for 3.5E back in the mid-2000s.
It's certainly not everyone's cup of tea, but I can see how that could make for some interesting dragonborn characters in 5E.
I want to say it was Unearthed Arcana but I'm not fully sure and don't have those books handy to check.