There are 9 human ethnicities mentioned in the PHB (pages 30-31): Calishite, Chondathan, Damaran, Illuskan, Mulan, Rashemi, Shou, Tethyrian, Turami.
PHB says (under "Human Names and Ethnicities" on page 30):
In the Forgotten Realms, nine human ethnic groups are widely recognized, though over a dozen others are found in more localized areas of Faerûn. These groups, and the typical names of their members, can be used as inspiration no matter which world your human is in.
Then SCAG (pages 100-112) mentions another 10: Arkaiun, Bedine, Ffolk, Gur, Halruaan, Imaskari, Nar, Shaaran, Tuigan, Ulutiun.
SCAG says (under "Human Ethnicities in Faerûn" on page 100):
Nine human ethnicities in Faerûn are detailed in the Player's Handbook. Several other noteworthy groups of humans are discussed here. Some are significant minorities in regions or nations that border the North, while others are prevalent in parts of the world far from the Sword Coast.
The wording of these quotes implies (at least, the way I read it) that all 19 of the listed human ethnicities exist exclusively in the Forgotten Realms (note that I'm equating Faerûn with the Forgotten Realms; this may be an incorrect assumption on my part). I am also under the impression that the Forgotten Realms is the default setting for 5e, hence why the PHB includes such ethnicities and quotes relating to the Forgotten Realms.
However, other settings for 5e exist; Eberron, Greyhawk and Dragonlance, for example (I don't know if there are any more major settings; these are the ones mentioned in the back of the PHB and SCAG, at least). Do any of these human ethnicities also exist in those settings, or are they exclusively a Forgotten Realms thing? And if the latter, I'm curious to know what human ethnicities do exist in these other settings.