No, Layer-2 maps work for non-Cisco devices as well. You might sometimes encounter the error as, "Device Mapping does not exist for this device" when trying to draw network maps for non-Cisco devices. To get the Layer-2 maps for other vendor switches, it must meet the following criteria:
At first OpManager checks whether the given seed device is a Router or L3 Switch based on the below criteria,
1. The switches must support SNMP protocol
2. Must have the BRIDGE-MIB implemented (most vendors support this MIB)
3. "ipForwarding" (OID - .1.3.6.1.2.1.4.1.0) for the device must be set to 1.
4. The device should have at least two or more interfaces (OID - .1.3.6.1.2.1.4.20.1.1).
If you still encounter the error, it is due to OpManager using RFC1213 and ipRouteTable to create the maps. This RFC has been deprecated and has been replaced by RFC2096 and ipCidrRouteTable. This can be replicated with Mib Browser. Try to see if your device is compliant with RFC1213 or RFC2096.