There is a not-yet documented feature in the latest GW OS, called ChirpStack UDP Bridge. It implements the Semtech UDP protocol and it could be used to forward data to TTN. You can run it next to the ChirpStack Gateway Bridge:
- Configuration:
/etc/chirpstack-udp-bridge/chirpstack-udp-bridge.toml - To start
/etc/init.d/chirpstack-udp-bridge start
(it does not start automatically on boot)