Going to add some more info, for the record.
For me, having docker running at the same time was no problem.
This solved it for me! ufw was blocking dhcp requests. The solution was:
sudo ufw allow in on lxcbr0
source: Archwiki: Linux containers#Firewall considerations
You can check this with:
sudo ps awux | grep dnsmasq
source: Github: canonical/lxd#1298