You can install an "Ubuntu" on OVH, but the kernel is a modified kernel. When you try to install standard services that are meant to work with Ubuntu, they do not work with the "OVH Ubuntu".
Apparently, Ubuntu contacted OVH to make the Ubuntu kernel closer to the stock Ubuntu kernel but OVH did not bother to do anything about it.
Then, Ubuntu told them that they break the trademark and one of the things they can do is get a license for the existing messy "OHV handicapped ubuntu", so that they keep providing this mess.
At that point, the founder of OVH went on twitter and a shitstorm ensued.
The whole affair reflects badly on the OVH founder. But many people will keep another impression in their mind.