I think virt-manager maybe too high up the stack for this dependency. I mean, it doesn't depend on seabios either - but that gets installed through the dependency chain. It also isn't possible for an architecture-independent package to depend on the correct EFI firmware package for the target architecture (e.g. x86 wants ovmf, but arm64 wants qemu-efi-aarch64).
I propose we reassign this to qemu, and ask that: 1) qemu-system-x86 bump the ovmf relationship from suggests to recommends. I wonder if the "suggests" decision was made back when edk2 was non-free? 2) qemu-system-arm replace the "qemu-efi" recommends with both "qemu-efi-aarch64, qemu-efi-arm". qemu-efi is now just a dummy package that depends on qemu-efi-aarch64. -dann