Do you have the UnDP you used to pull SNMP from the Dell iDRACs?
What's the question here?...
Dell iDracs support SNMP just like many other devices. As simple as enabling it.
Is there something specific you need to monitor that's not in the SolarWinds MIB database or showing up in list resources?
For a UNDP (Universal Device Poller) you'll need to know the OID (by doing an snmpwalk or otherwise) of the statistic you're looking for.
Just trying to point you in the right direction.
Sounds like you're looking for a list of compatible oid for the Dell iDRACS. This may help
Free IDRAC-MIB-SMIv2 SNMP MIB Download - Free MIB Download - Search MIBs - OiDViEW
I did create a Universal Device Poller that can grab a fair amount of information directly from the iDRAC.https://thwack.solarwinds.com/content-exchange/network-performance-monitor/m/universal-device-pollers/3303