That means that you have an existing DNS or DHCP server running on your machine which is binding all interfaces, preventing LXD from listening on lxdbr0.
sudo netstat -lnp | grep ":53 " should show you what it is (it’s often bind9/named).
Once you figure out what it is, you have two options:
- Remove that conflicting DNS server (if you don’t actually need it)
- Configure it to only bind to the interfaces you actually need it on