(In order of population size): Humans, Halflings, Dwarves, Orcs, Goblins, Gnomes, Hobgoblins, Bugbears, Elves, Dragonborn, Tiefling, Half-elves, Half-orcs, and smaller clusters of races like Goliath, Firbolg, Lizardfolk, Tabaxi, Warforger, Leonin, etc.
Generally, the PHB races, "monstrous races", and whatever people want to play although they might be more "unique" or "unheard of" individuals. There are very few races I simply won't allow.
But I warn players if they will likely face issues from the commonfolk if they choose certain races... such as yuan-ti, tiefling, dragonborn, monstrous races (orc, goblin, etc.). While folk of these races can be good and part of the civilized world, certainly, in new areas they might face hostility, mistrust, etc. I am not a fan of "everyone loves everyone
kum-ba-yah love-fest games." I don't play in them and certainly won't run one.