You can find several threads here about such conflicts with port 53.
In you specific case it looks that lxdbr0 has IPv6 as well, and as you say, named binds to ::::53.
If you do not need IPv6 in the containers, the disable it and try again. If it works now, the you know where the problem is.
The error that you get, does not start LXD’s dnsmasq, hence no name resolution in the containers.