It’s not an essential package rather it is just there to pull the following packages
bridge-utils dnsmasq iptables-nft edk2-ovmf libvirt netcat qemu-desktop radvd
virt-viewer virt-manager
via the dependency tree it creates. You can remove this meta package and install these packages individually, or forcefully remove only virt-manager-meta and mark it’s dependencies as explicitly installed so that they are not marked as orphans on your local system package database, but that just seems to be a duplication of work to me.
In your original post I didn’t see any PGP keys failing though? Could be a little more specific. What methods have you tried to resolve this issue?
Since the package has been orphaned it’s essentially no longer going to be updated unless someone picks it up on AUR again. So the best way to deal with it in my opinion is to remove it. However, you can still keep it if you feel it’s necessary. The only case I can think this package is necessary is if you are using openfortivpn.
The only issue post removal of this package was reported here along with a solution that didn’t even need this package.