It sounds like you don't have the GD extension installed. I don't use Ubuntu any longer, but I think it may be named php5-gd,...
How I converted a VMware VM to KVM
There's lots of info on the net on achieving that, but I found it a bit too scattered, and had to combine instructions from...
kvm
KVM Guest Drivers for Windows 2018 Overview This page describes how to obtain and use virtio drivers for Windows virtual machines running on KVM, and additional...
How to disable SSH timeout
How to install Xfce on Ubuntu