The variant is detected automatically: JA4 (TLS client), JA4S (TLS server), JA4H (HTTP client), JA4X (certificate), JA4T (TCP), JA4L (light distance) and JA4SSH. JA4T and JA4L share their format with their server counterpart — prefix the fingerprint with JA4TS: or JA4LS: to decode it as a server fingerprint.