Turns out most clones are broken in one way or another. For example, the Digital Ocean S3 Clone forgets the file Mime Type, so our brotli compressed JS is served as plain text and it breaks Discourse completely. So there is no big howto guides, because the experience was awful as a few months ago and everything is changing very rapidly.
I plan on doing a complete check on the ScaleWay offering next week, and write a #howto if it works.