Hi,
Talking to the development team, they have an experience with SAP RFC, see slide 22:
https://4js.com/files/documents/08%20-%20WW_TAC_2016_Genero_Report_Writer.pdfThey build a Java call to the JCO connector.
We can provide samples if you are interested.
Then with Genero, you need to use Java bridge with IMPORT JAVA.
An alternative is to enable SAP SOAP/REST interface so you have similar calls to SAP RFC but using web services (GWS).
Best regards,
Sisa.