Unfortunately I'm running into this bug as well on the latest version of XCP-ng. Regardless if running the console from XCP-ng Center or Xen Orchestra. It's a Windows Server 2019 VM (used Windows template) and I'm trying to boot from a Linux ISO in the virtual optical drive mounted to the Windows VM. I've tried using Ubuntu Desktop, Clonezilla and Rescuezilla. Same scrambled screen/console.