To me sounds like according to my understanding of the article one needed to set virtualisation.libvirtd.allowedBridges
to what is deemed “default” (“virbr0” in the article again).
Some links around here discussing the bridge interface workings:
- Networkd + libvirt + bridged networking -- how? - #5 by sorki
- Bridged VM networking setup - #3 by sperbsen
- Network bridge with static IP on host - #5 by barna
HTH