With this week's scheduled maintenance, we're making Antorus, The Burning Throne available to cross-realm groups in Mythic Difficulty.
Additionally, you'll now see Mythic Antorus in the selections in Group Finder.
To join a public group for Mythic Antorus, just open Group Finder (hotkey: i), select 'Premade Groups', then 'Raids-Legion', then click on "Find A Group". That returns a list of many public groups that are available to you. Start typing 'Antorus' into the search bar at the top, and you'll be prompted to select a difficulty.
Best of luck would-be Titanslayers!