I have the same question, we used to be able to use the web service authentication method + OData to access the BC cloud data, namely: user name + web service access key. But recently, MS decided to deprecate this method. the alternative is to use the AAD service principle and key.
- Find the OData URL, e.g. : https://api.businesscentral.dynamics.com/v2.0/xxxxxxxxx-6592-46f6-ba60-xxxxxxxxxxxxx/Benben10-Live/ODataV4/Company('Benben10')/bin
- Setup a linked service in a data factory or synapse using an OData connector. fill the details as follows:
the service URL example https://api.businesscentral.dynamics.com/v2.0/xxxxxxxxx-6592-46f6-ba60-xxxxxxxx/Benben10-Live/ODataV4/
here is a super detailed web page to create a service level credential for access BC with out using Office 365 user name and password authentication.
https://vjeko.com/2019/02/16/how-do-i-really-set-up-azure-active-directory-based-authentication-for-business-central-apis/#comments