pfSense (2.5) VM and VirtIO Networking fail - did i miss a memo?

Hi! I’m trying to virtualise pfSense on my home server (Ubuntu 20.04 LTS, libvirtd, virt-manager client GUI). I intend to expose pfSense to an isolated “services” interface, which is a virtual bridge (virbr0) on the Ubuntu KVM host.

I expect to see a vtnet interface inside the pfSense guest - but i don’t!

pciconf -l # on the pfSense VM

…doesn’t return any virtio network devices. However, the same command on my OPNsense VM produces at least 5 items.

What am i doing wrong, am i?
Does pfSense do something wrong?

Why does my OPNsense VM just do it? (i didn’t test a current version of OPNsense on the same KVM host [yet], but the VM on my old home server just does it.)