In the article Sav Malagán Returns and More Concept Art on Star Wars: The High Republic Show 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"
