can you do a check with an image downloaded from the images: repo ? these images do not have the cloud-init features. If it works then, all you have to do is to find the incantation to disable the cloud-init network setting when connected to a bridge. That’s just an idea, I’m not using anythink like your config myself.
edit: thinking twice, even if these images do not have cloud init, they could have still default dhcp networking. It’s quite common on standard distros.