I'm a big fan of GNOME Boxes. The developers put a lot of care into the UI design and into choosing sensible defaults so most things work well out of the box. However, there are some kinds of advanced tasks that can only be done via virt-manager. I doesn't happen very often for me but when it happens it can be useful to know how to use virt-manager to configure the VMs that GNOME Boxes created.

https://blog.agchapman.com/configuring-gnome-boxes-vms-using...

Virt-manager

+1 for virt-manager.

But you know what bothers me? Virt-manager is mature and feature-complete, and RedHat has discontinued it in favour of cockpit.

Cockpit is cool and I like it, but it's not as complete as virt-manager.