These models will be ready for ordering by Q3 2020 so, as temporary workaround, you can refer to Naked Models which mean the same machines as standard but without ABB image and all customizations (click here for further info).
All machines in this page are present for preliminary knowledge but the final ordering setup is still under definition and machines will be available by end of Q3.
Furthermore, another option is virtualization: it is possible to purchase models already present in the other section but without OS (e.g. Dell PowerEdge R640XL and HPE ProLiant DL380 Gen10) then to procure the OS separately, accordingly to the guideline of Windows 10 Procurement available at this link.