Forum Discussion
License requirements for retention policy OneDrive for Business
That's the issue - they don't enforce licensing requirements, so some functionalities will work even though you might not be properly licensed for them. In general, all the compliance features have traditionally required E3 or the equivalent ExO/SPO Plan 2, and I don't believe this has changed. It's very hard to find any document that actually mentions this however, so I guess if you want an official answer you should open a support case.
Pooya Obbohat : The "modern" Retention Framework is part of the Security and Compliance Center.
See the service description: https://docs.microsoft.com/en-us/office365/servicedescriptions/office-365-platform-service-description/office-365-securitycompliance-center
According to the service description retention policies are licensed in most plans.