The upstream virt-manager project including the virt-manager user-interface is still being maintained, but Red Hat Enterprise Linux 8 has decided to deprecate the virt-manager UI moving forward.
With the recent RHEL 8.2 release it turns out the virt-manager UI is deprecated. This is the common graphical user interface for managing VMs on the likes of KVM and Xen with libvirt and has been quite common for a decade. Virt-manager has been around for a while for those wanting a means of easily creating, managing, and viewing virtual machines running on Linux.
Red Hat is deprecating the Virt-Manager interface in RHEL in order to push along Cockpit. Cockpit is the web-based server management interface that offers a lot of functionality from physical server management to network management, application management, SELinux handling, and also functionality around containers and virtual machines.
From Cockpit you can view VMs and have similar functionality to virt-manager. It appears that Red Hat is wanting to present Cockpit as the unified user-interface for Red Hat Enterprise Linux as opposed to the host of different utilities that may or may not be known to users/administrators.
The virt-manager interface is likely to remain available for the remainder of RHEL 8.x releases while likely will be removed in RHEL9. But at least if it’s dropped from RHEL9, given the popularity of virt-manager it’s quite likely to appear in the EPEL repository of extra packages. Outside of RHEL, virt-manager is still being maintained.
More details on the virt-manager UI deprecation in RHEL via this personal blog post by virt-manager lead developer Cole Robinson of Red Hat.