Info about Cloud Identity Free: https://support.google.com/cloudidentity/answer/7319251
Steps for adding Cloud Identity Free: https://support.google.com/cloudidentity/topic/7555155
You will only lose access to Gmail and Calendar, though make sure you migrate email and calendar before moving to Cloud Identity Free.
Disclaimer: i haven't followed the steps myself since i'm paying for a personal Workspace account since a few years ago.