“Ethertype unknown” means that Suricata doesn’t recognize the layer 2 protocol. Suricata knows about most layer 2 protocols – see the full list in the source code file decode.h and/or `decode-ethernet.h
According to chatgpt — I cannot vouch for its response, but it looks reasonable.
It’s an LLDP advertisement from a device with chassis MAC D8:EC:E5:C1:CC:58, sent out of a locally labeled port “22”, with a 120-second TTL, using the standard LLDP multicast destination. (Typically there’s an End-of-LLDPDU TLV 00 00, which just isn’t shown here.)