For my "I'm not actually trying to design this, it's just ideas I have" pseudo-heartbreaker, I wanted to go for giving every race four subraces, except humans where I was only able to justify three.
0. Human aka "wanderfolk": Earthfast, Starbound*, and Dual-Blooded (covering all the various half-something hybrids.)
1. Belua aka "beastfolk": Minotaur, Tabaxi, Lupin, Cervid. A people defined by their diversity of form, while still being one species.
2. Dragonborn aka "drakefolk": Imperial (city), Austral (desert), Tropical (jungle), Littoral (coastal/waterside.)
3. Dwarves aka "stoutfolk": Gold (mountain), Copper (forest), Tin (ocean), Iron (cavern.)
4. Elves aka "feyfolk": Sun/eladrin, Moon/(wood) elf, Star/drow, Void/shadar-kai.
5. Forgeborn aka "metalfolk": Warforged, Envoy, Archivist, Sower.
6. Halflings aka "hinnfolk": Lightfoot/arboreal, Stoutheart/plains nomads, Cragstep/caves, Ghostwise/deeps.
7. Orclings aka "stormfolk": Orc, Goblin, Hobgoblin, Bugbear. A similar diversity of form to belua.
8. Planetouched aka "pithfolk": Aasimar/celestial, Tiefling/fiendish, Genasi/elemental, Deva/astral.
9. Satyrs aka "mirthfolk": Spring, Summer, Autumn, Winter.
*"Earthfast" would cover literally all IRL humans and their fantasy equivalents. Humans that live on ordinary, Earth-like planets or planes. "Starbound" is for things like slann/elan: humans Weirded™ by exposure to the eldritch powers of the far reaches of space or otherwise made a bit alien by various energies, while still being properly human.
I would have liked to come up with a fourth human option, but I racked my brain for hours and hours and never hit on anything interesting, let alone passable given the many, extremely fraught implications.