i found in the syslog from one off the nodes:
2019-01-24T13:35:43.145664+01:00 ha-idg-1 crmd[20846]: warning: Compile-time support for crm_mon SNMP options is deprecated and will be removed in a future release (configure alerts instead)
I think that's a clear statement. We shouldn't waste our time with something deprecated. I will switch to alerts.