Thank you very much Rodolfo! 
This patch works for routers already created.

Some debugs below:


Nov 17 17:48:47 os-infra-1-neutron-server-container-819795c0 neutron-server[1242]: 2022-11-17 17:48:47.301 1242 DEBUG futurist.periodics [req-2e9d417a-0eaf-4628-b061-f6800dc3e42a - - - - -] Submitting immediate callback 'neutron.plugins.ml2.drivers.ovn.mech_driver.ovsdb.maintenance.DBInconsistenciesPeriodics.create_router_extra_attributes_registers' _process_immediates /usr/lib/python3/dist-packages/futurist/periodics.py:676
Nov 17 17:48:47 os-infra-1-neutron-server-container-819795c0 neutron-server[1242]: 2022-11-17 17:48:47.508 1242 DEBUG futurist.periodics [req-2e9d417a-0eaf-4628-b061-f6800dc3e42a - - - - -] Periodic callback 'neutron.plugins.ml2.drivers.ovn.mech_driver.ovsdb.maintenance.DBInconsistenciesPeriodics.create_router_extra_attributes_registers' raised 'NeverAgain' exception, stopping any further execution of it. _on_done /usr/lib/python3/dist-packages/futurist/periodics.py:713



MariaDB [neutron]> 
MariaDB [neutron]> select * from router_extra_attributes;
+--------------------------------------+-------------+----------------+----+----------+-------------------------+
| router_id                            | distributed | service_router | ha | ha_vr_id | availability_zone_hints |
+--------------------------------------+-------------+----------------+----+----------+-------------------------+
| 122a76ab-5d77-4eb1-a0c2-9cb1816d39b7 |           0 |              0 |  0 |        0 | []                      |
| 6a20498b-9120-4d5b-8cb7-d02e6d5eac02 |           0 |              0 |  0 |        0 | []                      |
+--------------------------------------+-------------+----------------+----+----------+-------------------------+
2 rows in set (0.001 sec)

MariaDB [neutron]> select * from routers;
+----------------------------------+--------------------------------------+---------+--------+----------------+--------------------------------------+-------------+------------------+-----------+
| project_id                       | id                                   | name    | status | admin_state_up | gw_port_id                           | enable_snat | standard_attr_id | flavor_id |
+----------------------------------+--------------------------------------+---------+--------+----------------+--------------------------------------+-------------+------------------+-----------+
| 26dc9f1085fa4688a08e803cfb374540 | 122a76ab-5d77-4eb1-a0c2-9cb1816d39b7 | router2 | ACTIVE |              1 | 5745084a-9313-4eba-93b1-44f86018ccb8 |           1 |              374 | NULL      |
| d11daecfe9d847ddb7d9ce2932c2fe26 | 6a20498b-9120-4d5b-8cb7-d02e6d5eac02 | router1 | ACTIVE |              1 | f767ae07-5856-4a76-8e7b-dfe675ffac56 |           1 |              368 | NULL      |
+----------------------------------+--------------------------------------+---------+--------+----------------+--------------------------------------+-------------+------------------+-----------+
2 rows in set (0.001 sec)

MariaDB [neutron]> 


root@jump-host:~# openstack bgp speaker list advertised routes bgpspeaker
+----------------------+-----------------------+
| Destination          | Nexthop               |
+----------------------+-----------------------+
| 2001:db9:1234:1::/64 | 2001:db9:4321:42::22d |
| 2001:db9:1234::/64   | 2001:db9:4321:42::70  |
+----------------------+-----------------------+