Which component is similar to an EVPN instance?

An MPLS label is a short, fixed-length identifier used for forwarding packets within an MPLS network; it is a forwarding mechanism, not a logical isolation construct like an EVI or VRF.

An IGP router ID is an identifier for a router within an Interior Gateway Protocol (IGP) domain; it identifies a router, not a customer-specific service instance.

Both EVPN instances (EVIs) and VRF instances provide multi-tenancy by creating isolated forwarding contexts on network devices. An EVI isolates MAC address tables and Ethernet forwarding domains for different EVPN services, while a VRF isolates IP routing tables and IP forwarding domains for different IP VPN services, achieving similar segmentation goals.

A router distinguisher (RD) is used in MPLS VPNs to make customer VPN routes unique in the global BGP table, but it is a prefix to a route, not an instance of logical isolation like a VRF or EVI.