I don't know anything about dedicated servers (I know, I'm a noob) and almost every dedicated server is empty, and I want to play a particular mod. Is there a way to host a local game so that I can host a mod and people can join the game?

If you know people you can ask them to join on your external ip address and you can host a private match

otherwise you can just host a server on port 28961

You do know you can host a server on your PC, right ?