Above configuration has been around and had worked till recently (possibly through dist upgrade 18.04 to 21.04).
Is there an easier way to route all internet traffic from public IP to container IP, or just selected ports forwarding?
I saw the introduction of Floating IP addresses
Does it work on unmanaged bridges as well?
Unmanaged, because managed LXD is making its own entries in ip tables which sometime interfere with other config as well as not easy to control the dnsmasq config. Running multiple dnsmasq instances with each own config, resolve, hostsfile is easier than passing all those 50+ dnsmasq config parameters through lxd dnsmasq service initialize.