Microsoft added text to the October 2023 Product Terms confirming that if a customer has enabled Extended Security Updates through Azure Arc they may use the updates on licensed Disaster Recovery servers and in Dev/Test environments.
Find the terms here: https://bit.ly/3Y6xsac, and note that the same rules apply for the traditional 1-year ESUs, the terms of which are here: https://bit.ly/46ldV8W.
Microsoft announce that special discounts are now available for Windows Virtual Desktop used within an Azure dev/test Subscription. Find the announcement here: https://bit.ly/2K0C6Sg. There’s also language added to page 56 of the April 2020 Product Terms document detailing the use rights of Windows Virtual Desktop in dev/test environments. Find the Product Terms documents here: http://bit.ly/MSproductterms.