) in the top 50 in population (according to the 2020 census) will Waymo serve with publicly available driverless taxi rides at the end of 2026? 

Rides must be paid, driverless, and available to the general public (i.e. not just employees or any sort of trusted tester program. But if there is a waitlist to manage demand that still counts).

As of mid-2024, Waymo currently serves the SF, LA, and Phoenix metro areas and is planning to expand to 

See similar question (slightly different criteria) for 2025: