as you described, it is not possible to use the SAP GUI for Windows with an SAP communication user. So you can’t use any SAP UI, including the SAP GUI scripting. All you can do is to use RFCs (remote enabled function modules, RFM).
Yes, it is possible to use RFCs with UiPath. But RFCs are all without any proportion of UI, it contains only a technical interface. On the one hand you can use UiPath.SAP.BAPI package.
Or on the other hand you can use SAP dotNET Connection NCo to use RFCs.
Here an example how to use RFC_READ_TABLE.