Getting a bank charter and FDIC insurance is a huge undertaking, so neobanks are usually not actually banks. They are technology companies that have partnered with banks or are customers of banking-as-a-service providers (Hydrogen, Stripe Treasury, and similar).

The banking partners have their own bank charter and FDIC insurance, but the technology company itself does not. If you go to most neobank websites, you can scroll to the bottom and see a disclosure along the lines of "Banking services provided by The Bancorp Bank, N.A. or Stride Bank, N.A., Members FDIC".