How Do I install PVE if the VPS provider only offers Ubuntu 20?

Hello,

first of all, please only post in English (or German, in the appropriate sub-forum).

Installing Proxmox VE on top of Ubuntu is not supported. Check if you can upload a custom ISO, or use another VPS provider.

Hope this helps.
 
Generally, if custom ISO images are supported, there should be an option in the management interface to upload and attach an ISO image as a CD ROM drive to your VM. For details, please consult your hosting provider's documentation or technical support.