I sorted out the DHCP issue I saw yesterday. There was a discussion on this topic that was very helpful.
There was a checksum problem in the request for an address. The fix was to apply sudo ethtool --offload lxdbr0 tx off to disable checksum offloading on the bridged network in LXD.
This site has a nice description of the what that means:
Checksum offloading is usually beneficial as it allows the checksum to be calculated (outgoing) or verified (incoming) in hardware at a much faster rate than it could be handled in software.
Checksum offloading is broken in some hardware, particularly Realtek cards and virtualized/emulated cards such as those on Xen/KVM.
Anyway, turning it off allows FreeBSD to get an IPV4 address from the bridged network.