Have similar configurations in the form of e.g. iMST Lite GW, getting it onto V3 keeping UDP packet forwarder was easy - if you have similar config edit the local_config.json file associated with the active packet forwarder to simply change the target TTN server (eu1.cloud.thethings.network for EMEA), in my case IIRC it was in /opt/ttn-gateway/bin, if needed for your packet forwarder, swap the server key from current V2 version to a new one created in V3 (create API key - link as gateway… option) - basic ttn-zh/ iMST forwarder didn’t need one, tidy up any loose/un-needed lines in the code (I had none of issue in my basic iMST set up, vs some of my more complex Pi Based builds) and reboot - should be good to go (Make sure Require Authenticated Connection is unchecked in General Settings of GW’s V3 console)