According to a recent announcement, Google will not build or use identifiers, while doubling down on Federated Learning of Cohorts (FloC) as as a way for an advertiser to reach their intended audience.
After doing some testing, Google said that “advertisers can expect to see at least 95% of the conversions per dollar spent when compared to cookie-based advertising.”
You might want to consider gathering first party data from sources like rewards programs, email signups and the such, as it can help you learn more about your customers.