The link to join is Discord Simutrans Server (https://discord.gg/KuaVWycD9E).
"Discord is a proprietary freeware VoIP application designed for gaming communities."
Feel free to jump in and start discussing Simutrans and games in general (both as a gamer and a developer). There just a few channels and roles right now, which should be more than enough. Nobody will get "pruned" for not talking. You can chill and just be a spectator or talk as much as you want.
Edit: The new link will not expire!