Call SAP OData Service in Logic App through On-Premise Data Gateway

Julia2195 consider using a REST custom connector with auth. OData is a REST endpoint. Logic App support REST both as native HTTP request as well as wrapped in a convenient custom connector, the later which may further make use of the On-Premises Data Gateway you noted you needed to access the network where you SAP OData endpoint is present.

https://docs.microsoft.com/en-us/connectors/custom-connectors/

https://docs.microsoft.com/en-us/learn/modules/logic-apps-and-custom-connectors/

https://www.serverless360.com/blog/custom-connectors-in-azure-logic-apps

You can also use Azure Logic Apps Integration Service Environment (ISE), then you bring Logic App in the same network as SAP and can just use HTTP REST actions - no gateway required:
https://azure.microsoft.com/en-us/blog/announcing-azure-integration-service-environment-for-logic-apps/