Frame Relay - is it a relevant technology anymore
Frame-Relay is a technology that was very popular in the 1990s as it was a cheaper alternative to leased lines.
Over the decades, it declined in use and has been largely replaced by other WAN technologies including MetroEthernet, MPLS, DSL, Cable, VPNs, wireless bridges, and fiber optic links, or some combination of several of these technologies. The choice of the WAN technologies used depends upon availability, performance, and cost, and today, most of these mentioned technologies outperform Frame-Relay, are cheaper, and more widely available.
Frame-relay as a technology is no longer found in Cisco exams, however, features such as OSPF network types as well as EIGRP authentication per neighbor are indeed valid. These features can only be labbed up using a non-broadcast network topology and Frame-relay is the most convenient. So although it is not a topic in the exams, it is still necessary to learn other features.