@odie A bot doesn't require the lobby to run. If it can't connect to whatever lobby address/port you specify, it will print an error to the console, but otherwise will continue to operate normally.
However, it's not exactly clear what you're trying to do. If you simply want to host a game in which you will participate (and want to bypass the lobby), you can just use the Host Networked Game command from the main menu. The only reason I can think why you'd want to host a private bot that doesn't connect to the lobby is if you want to provide a server for your friends for games in which you're not participating. That is, so your friends can play against each other:
without you as an active player,
without having to use the lobby, and
without you having to run the full GUI on your desktop.
BTW, from a security perspective, if you're going to run a bot that's reachable from the Internet-at-large and running all the time, I'd recommend running it using a non-administrative account. In fact, if possible, you should create a separate account to run it so that, if it happens to get compromised, the damage an attacker can do to your host will be limited.