Vertiv's rack PDU line (formerly Liebert) uses its own MIB, distinct from the cooling-unit MIB used on Vertiv's CRAC/CRAH lineup.
Under the unit's Network Settings, enable SNMP and set a community string or SNMPv3 credentials, the same pattern as APC and Eaton's equivalent PDU lines.
If the same rack also has a Vertiv CRAC or CRAH cooling unit, that's a separate device with its own SNMP agent and MIB; see the environmental monitoring guide for cooling units specifically.
Linivo polls per-outlet or per-bank load depending on the model, plus the unit's own temperature and humidity sensor if it has one built in.