There's a lot of open source UIs and enterprise-grade provisioning UIs, both native and web, available for it. libvirt also has first class support to convert and import from vmware images.

For our small startup, we use cockpit, but there's also a KubeVirt integration for kubernetes daemons/UIs. And I heard Foreman is a good alternative, too.

[1] https://libvirt.org/apps.html

[2] https://cockpit-project.org/

[3] https://theforeman.org/