I seem to have more luck using the RAK software on my pi with the semtech udp for the 2245 rather then the chirpstack OS mqtt using concentratord. Not sure why, i might try latest version again and make sure I didn’t miss configure something.
A little hack you could try, use rak software and setup the gateway with sudo gateway-config and fill in for details for your GW, then chose TTN -> once done go edit the global.json to point the UDP to your chirpstack ns UDP rather then the TTN router/port update with your ipaddress/domain and port by editing and saving that file. Restart pi and you should be good.
Using the RAK software…
/opt/ttn-gateway/packet_forwarder/lora_pkt_fwd/global_conf.json
head down to bottom of file, in the last block…
"gateway_conf": {
"gateway_ID": "0000000000000000",
/* change with default server address/ports, or overwrite in local_conf.json */
"server_address": "< YOUR IP/DOMAIN HERE >",
"serv_port_up": <UDP PORT>,
"serv_port_down": <UDP PORT>,
/* adjust the following parameters for your network */
"keepalive_interval": 10,
"stat_interval": 30,
"push_timeout_ms": 100,
/* forward only valid packets */
"forward_crc_valid": true,
"forward_crc_error": false,
"forward_crc_disabled": false,
/* gps enable */
"gps_tty_path": "/dev/ttyAMA0",
"fake_gps": false,
"ref_latitude": 10,
"ref_longitude": 20,
"ref_altitude": -1,
"autoquit_threshold": 20
}