If you want to temporarily enable FLoC for some reason, start Chrome with the following flags (from [0]):

  --enable-blink-features=InterestCohortAPI --enable-features="FederatedLearningOfCohorts:update_interval/10s/minimum_history_domain_size_required/1,FlocIdSortingLshBasedComputation,InterestCohortFeaturePolicy"

[0]: https://developer.chrome.com/blog/floc/#try-out-floc-as-a-we...