Sam - can you confirm what version you are running and provide a traceback?
From what I can see the change that introduced multiple external gateways [0] is in 2023.2 and later.
$ git describe a221764751de05e42069f1c097b1025bd9c4fc52 23.0.0.0b2-53-ga221764751
[0] https://review.opendev.org/c/openstack/neutron/+/873593
Sam - can you confirm what version you are running and provide a traceback?
From what I can see the change that introduced multiple external gateways [0] is in 2023.2 and later.
$ git describe a221764751de05e 42069f1c097b102 5bd9c4fc52 0b2-53- ga221764751
23.0.0.
[0] https:/ /review. opendev. org/c/openstack /neutron/ +/873593