Afaik Billing in sandbox is currently only possible for Azure Plan subscriptions, but as I understood there are plans to enable this also for other license types in the future. Do you have access to the SDK & API group in this yammer network: https://www.yammer.com/cloudpartnercommunity/#/threads/inGroup?type=in_group&feedId=6589502 ? The engineers and PMs are quite active for questions from Partners and CPVs in there.
The community here is more specifically on Security guidance reg. the MFA requirements
Kind regards, Janosch (Note: Leaving role as of March 2023, don't expect further answers. Connect with me via LinkedIn: https://linkedin.com/in/janoschulmer)
