The VIDM Connector logs appears to show successfull directory sync events. Of course its not possible to view the directory itself from vRSLCM any longer. The User Management tab in vRLCM still shows the groups and changes can be made there.
I've just had a look at the vRLCM vmware_vrlcm_log and it shows the failures when attempting to enumerate our directory....
Failed to list directories on vIDMServer{host=hostname.local, tenant=null
java.lang.IllegalArgumentException: Class com.vmware.vrealize.lcm.vidm.common.dto.ad.sync.SyncRunResultsDTO["violationbytype"]java.util.LinkedHashMap["addUsersToGroup"].....
Looks like an unhandled exception in jackson-databind-2.10.2.jar from the rest of the error.
We have a pretty simple out of the box directory with nothing special in it whatsoever so if our environment is causing issues like these it very likely to be occurring elsewhere I'm sure!.