On a fresh Ubuntu 23.10 (beta) installation, the virtual machines area in Cockpit appears to be broken. All package requirements were installed.
Accessing the area shows the following error message:
Virtualization service (libvirt) is not active
To fix the error, add the libvirtdbus user to the libvirt group:
sudo usermod -a -G libvirt libvirtdbus
Reboot the computer/server and the problem should then be resolved.