Life is Strange 2 will be removed from Australian digital storefronts, according to the official Life is Strange Twitter account. As you've probably guessed, this move has been prompted by the Australian Classification Board: it's currently reviewing the game's age ratings.
As a result, the unavailability will only last for "approximately" two weeks. At the time of writing it's still available on Steam, and that's likely to last until Wednesday Australia time.
Here's the full statement:
This situation is temporary and only affects Australian digital storefronts. We will restore service asap and will keep you updated with any developments. Already installed LiS2 content will not be removed from your device during this period and will still be playable.September 9, 2019
At a hunch, I'd guess this is happening in order to rate each additional DLC and post-launch addition to the game: for an episodic game like Life is Strange 2, the vanilla launch build is obviously only a tiny part of the game as it stands right now. Recent examples of DLC triggering a ACB reappraisal include Kingdom Come: Deliverance and We Happy Few, which are both now available to purchase after a temporary delisting on digital storefronts.
The ACB has been in the headlines a bunch lately, mostly thanks to the belated (and frankly quite amusing) ban of DayZ. It fell afoul of Australia's ratings board due to DLC that hadn't even made it to the game yet. But the game is safely available to purchase now.
Thanks for the heads up, Kotaku.