SharePoint 2019 Migration

Hi,

Currently we are doing SharePoint migration from 2013 to 2019.

the existing portal is Anonymous access with FBA implemented.

We need your suggestion/advice here.

In newly migration site

we are configured with AAD form AD but no SSO

Anonymous access is required

but how do we handle this FBA for external users? shall we go with same FBA concept?

or B2B ? since we are moving from AD to  AAD.

If B2B is the correct way, please provide the reference, how to implement?

or

If need to go with SSO, need advice how to provide anonymous access?

Regards,

Britto