Licensing a Dataverse environment for external users

Looking for some advice and opinions please.

This is for a standalone Dataverse environment. Not Dynamics 365, or Power Apps, or Power Pages.

The question is about using a Dataverse environment with the native Dataverse web APIs, where a portal is developed (not Power Pages) that allows the external users to interface (read/write) data.

My opinion is that because this is not Dynamics 365 and Power Pages are not being utilised to facilitate the access then there is no requirement for user (D365, Power App, or Power Pages capacity) licensing.  I would still need Dataverse capacity licenses, but that is all.

Appreciate any thought and insights.

Thanks,

Nick