If it’s a linux/bsd machine, even a mac you can use rsync. Rsync is really powerful.
Duplicati for file level. Veeam also has a free agent as well.
The Veeam free is a excellent easy to use and very powerful BU tool. It is also a disaster recovery tool check out its features, incrementals rolled into synthetic fulls verified file and directory recovery up to full system restore.
Doesnt look like Veamm supports Xen, xcp-ng unfortunately.
Try the Linux bare metal Veeam since XCP-NG is Linux it should backup the entire host. Started to test a while back but got busy and the available server was shipped out for other demos.