libressl does not support SSL_CTX_set_ciphersuites.

src/conf.c

@@ -1180,11 +1180,11 @@ int config__read_file_core(struct mosquitto__config *config, bool reload, struct
 					log__printf(NULL, MOSQ_LOG_WARNING, "Warning: TLS support not available.");
 #endif
 				}else if(!strcmp(token, "ciphers_tls1.3")){
-#ifdef WITH_TLS
+#if defined(WITH_TLS) && !defined(LIBRESSL_VERSION_NUMBER)
 					if(reload) continue; /* Listeners not valid for reloading. */
 					if(conf__parse_string(&token, "ciphers_tls1.3", &cur_listener->ciphers_tls13, saveptr)) return MOSQ_ERR_INVAL;
 #else
-					log__printf(NULL, MOSQ_LOG_WARNING, "Warning: TLS support not available.");
+					log__printf(NULL, MOSQ_LOG_WARNING, "Warning: ciphers_tls1.3 support not available.");
 #endif
 				}else if(!strcmp(token, "clientid") || !strcmp(token, "remote_clientid")){
 #ifdef WITH_BRIDGE

src/net.c

@@ -394,7 +394,7 @@ int net__tls_server_ctx(struct mosquitto__listener *listener)
 			return MOSQ_ERR_TLS;
 		}
 	}
-#if OPENSSL_VERSION_NUMBER >= 0x10101000
+#if OPENSSL_VERSION_NUMBER >= 0x10101000 && !defined(LIBRESSL_VERSION_NUMBER)
 	if(listener->ciphers_tls13){
 		rc = SSL_CTX_set_ciphersuites(listener->ssl_ctx, listener->ciphers_tls13);
 		if(rc == 0){