Checking the network settings on the ubuntu:
sudo nano /etc/netplan/00-installer-config.yaml
Somehow the gateway was wrong?
Also installing the Guest service:
Step 1: Log in using SSH
You must be logged in via SSH as sudo or root user. Please read this article for instructions if you don’t know how to connect.
Step 2: Install qemu guest agent
apt update && apt -y install qemu-guest-agent
Step 3: Enable and Start Qemu Agent
systemctl enable qemu-guest-agent
systemctl start qemu-guest-agent
Step 4: Verify
Verify that the Qemu quest agent is running
systemctl status qemu-guest-agent
casperse's post in VM having No internet access/network after moving to new Unraid Server? was marked as the answer