I think I may have fixed it, I'm not 100% sure but it's now been showing on the master server list consistently for over 12 hours, far longer than I've ever managed before. This is what I did. I couldn't find anything in /var/log/daemon.log or indeed /var/log at all (although there may of course be something hidden in there somewhere). However I managed to produce a log file by running the server with the following command:
$ openarena-server +exec debian_server.cfg +set dedicated 2 &> logfile.log
...EDIT: I take it all back I wasn't going mad, after 24 hours of it working, the server crashed for some reason and after restarting it it's not showing up in the master server again
. Here's part of the log, not sure if there's if there's anything wrong with it. Other than that, think I give up now
]Hitch warning: 1266 msec frame time
]Resolving 107.161.23.68:27950 (IPv4)
]107.161.23.68:27950 resolved to 107.161.23.68:27950
]Sending heartbeat to 107.161.23.68:27950
]Resolving 176.9.53.212:27950 (IPv4)
]176.9.53.212:27950 resolved to 176.9.53.212:27950
]Sending heartbeat to 176.9.53.212:27950
]Hitch warning: 589 msec frame time