Atlas policies
In the MongoDB atlas portal, there should be a way to configure policies across an organization. ie: policies to restrict users from creating clusters from certain cloud providers (ie: azure), restrict users from creating databases of a certain size, etc.

-
Amede commented
Without impacting the multi-Cloud feature, it should be good to restrict (via some policies) the creation of a MongoDB cluster to a single CSP (AWS, Google Cloud, Azure) which might be the only one the user will have displayed, and which would be for example the one from which the subscription is made.
For example, if my subscription is made on AWS, I would like to give the possibility of creating a MongoDB cluster only on AWS which in the case would be the only CPS displayed.