California and Nevada. From the first sentence of the article:

> Mercedes-Benz is the first automaker to gain approval to sell a Level 3 automated driving system in the United States; the first customer-owned S-Class and EQS sedans in California and Nevada equipped with the Drive Pilot system hit dealer lots this month.

Does level 3 not legally require an attentive operator in those jurisdictions?

Correct, and that is also answered very early in the article.