The simple thing are the maps, which are here: https://unrealarchives.com/ (not to be mistaken with unrealarchive.org)
The default gametype is unrealshare.coopgame.
Or other ones which float around, or are packed with the campaign itself.
The hardest thing is testing all campaigns to see what works with that gametype, and which are not.
That is, if you want to host multiple campaigns ofcourse.