in order to remove chassis from OVN N/S database I executed on every removed compute node:
apt -y purge nova-common ovn-common neutron-ovn-metadata-agent neutron-common rm -fr /etc/nova /var/lib/nova/instances /etc/ovn
If the removed compute node is also a gateway chassis one needs to remove the router port
in order to remove chassis from OVN N/S database I executed on every removed compute node:
apt -y purge nova-common ovn-common neutron- ovn-metadata- agent neutron-common nova/instances /etc/ovn
rm -fr /etc/nova /var/lib/
If the removed compute node is also a gateway chassis one needs to remove the router port