How can I set up CDC for Managed Postgres Instance on GCP?

Take a look in Google GCP docs: https://cloud.google.com/blog/products/databases/you-can-now-use-cdc-from-cloudsql-for-postgresql

Cloud SQL for PostgreSQL is a managed service, so it restricts access to certain system procedures and tables that require advanced privileges. In Cloud SQL, customers cannot create or have access to users with superuser attributes. https://cloud.google.com/sql/docs/postgres/users#superuser_restrictions According to my understanding, postgres instances require superuser privileges to create replication slots, and based on the documentation, I doubt Google provides this level of support. This prompted me to consider how I could perform incremental load using airbyte (Update and Insert) Please let me know if you have implemented this or something similar.

As you read from the documentation maybe using the managed instance you can’t use incremental reads.