AD Functional level at 2012R2
GC's are 2012R2 and one 2016
Added 2019 server, did dcpromo and said successful, but won't sync, dns, etc.
Errors with: the replication operation failed because of a schema mismatch between the servers involved
Ideas how to get around. We noticed that when trying to introduce 2016 RODC and 2019 RODC and now 2019 GC