I can also recommend kapper.net, second Proxmox Hosting Partner and also here in Vienna. Like OVH, they support the project with hosting services - the main difference is the company size - if you only trust a big company, go for OVH. If you want the flexibility of a smaller one, go for kapper.net.
So generally speaking, you should always choose hosting services from Proxmox partners as they actively support the project.