Azure used to bill themselves as the "open cloud". That's kinda gone from their marketing, but they are WAY more open than AWS.

Only OpenStack is fully open source and fairly feature complete, with a few dozen providers using the OpenStack platform.

OVH, who owns the largest datacenter in North America uses OpenStack, they're actually one of the largest contributors. Red Hat & IBM both seem to be really pushing private deployments as of late for their larger clients that already own large DCs.

Knowing that OVH uses a piece of software makes me want to never use that piece of software.

They are the worst quality cloud provider, IMO.

Definitly not the worst, but very far from the actually good ones for sure.