@smooki
g_gametype sd
You could look at the server config for a list of game types https://github.com/xerxes-at/T6ServerConfigs/blob/master/dedicated.cfg
Do not that this won't instantly change, you have to either load another map or do a map_restart for the game mode to change.
You can also find a list of maps in the config i posted above, the command for those is just
map mp_mapname
undefined
