How exactly do you check that the joining of the L2 tunnel to the bridge does not work? You’ve only shown the part of the configuration related to L2TP, but not the one related to other ports of the bridge. I’d suppose you want to use the CHR to provide an L2 tunnel to the remote site to some other virtual machines running on the same host like the CHR.
If my guess is correct, bear in mind that most virtualisation platforms prevent “MAC address spoofing” by default, so if you want to use a network interface of a VM as a port of a bridge, you have to explicitly permit MAC address spoofing in the settings of that virtual network interface, otherwise the virtual switch will drop frames with any source MAC addresses different from the CHR’s own one on that interface.