Thank you for the answer! Looks promising. So setting up a proper Travel URL like in your example will already override the gamemode, or is it just a parameter that is transmitted to the new level which I can then use to change the gamemode on the fly?
Sorry if I am missing obvious things here, but since I am still a little new to multiplayers this stuff is really a blackbox for me. Reading the compendium section on it helped only partially, as I didn’t understand half of it