In the article  [Sav Malagán Returns and More Concept Art on Star Wars: The High Republic Show][1] on the official Star Wars website, this is mentioned about Yaddle:

> The Force-user is the same species as Yoda and Grogu, and she'll play an important role by the end of Phase II.

As a sidenote, I found this page by simply Googling "Grogu species site:starwars.com"


  [1]: https://www.starwars.com/news/star-wars-the-high-republic-show-204-reveals