I’ve got the same problem here.
It looks like lookup_server_connector tries to update user data on lookup.netcloud.com. It hooks “User changed” and it looks like it’s also triggered if users synced from LDAP. Got around 300k entries in oc_jobs here (udated some days ago to NC14). The lookup.nextcloud.com server seems to be down.
All federation options are set inactive in admistrative options here. Why it is syncing ? “occ app:disable” doesn’t work für lookup_server_connector, so I removed the folder in apps and deleted all entries of the LookupServerConnector class in oc_jobs.
Filed a bug report: https://github.com/nextcloud/server/issues/13396