SAP has the BTP and all their different products, so IaaS is very much the issue for them and I doubt they have solved it without the help of Microsoft.
StackIT is Germanys best shot at a sovereign cloud currently. Basically a fork of OpenStack.
I very much doubt SAP has the competence to replicate this. I'll also bet those unnamed open-source technologies are mostly sprinkled on top of proprietary Azure tech, like the rest of their infrastructure.
I doubt thats the case.