There are two migration sections in 2.x:

Gateway migration: https://docs.redhat.com/en/documentation/openshift_container_platform/4.17/html/service_mesh/service-mesh-2-x#ossm-about-gateway-migration_gateway-migration

Route migration: https://docs.redhat.com/en/documentation/openshift_container_platform/4.17/html/service_mesh/service-mesh-2-x#ossm-route-migration 

These 2 sections need to be accounted for in the 2.6 to 3.0 Migration Guides, either via links to them, or moved to 3.0.