recommended max number of buckets....
There should be a recommended max number of s3 buckets and tests to support said number.
Leaving this as 'there is no maximum' invites problems for large deployments.
Client surveys, including statements such as 'Client X has deployed a cluster with N buckets successfully', also would help.
Issues such as https://tracker.ceph.com/issues/45630 have been discovered that limit the distribution of buckets in large deployments. Other similar issues could be discovered that affect this issue, and thus impose ancillary limitations.
We have only tested up to N buckets would also be helpful.