pg_subscription_rel
pg_publication_rel
have the relation part of the publication concerned.
OP has an issue to figure out if publication has a list of tables not in sync in subscription and has subscription broken.
there may be ways to query tables on subscriber dbs via dblink or fdw,
but there is no view of metric for individual relation level subscription to help figure out if it is broken.
I mean like for replication slots, we have an active flag to easily figure out issues with replication, but not with pub/sub.
I only used logical replication for upgrades, so not have little idea wrt ddl changes issues.
