Website translator here, I've seen quite a lot on the DLC for when the website goes up closer to release.
It will release on December 18th 2025.

It follows the protag and their friends as they discover mysterious portals or "distortions" created by Hoopa which lead into an alternate reality of Lumiose City.

I haven't seen any images but from what I've gathered its in a post apocalyptic future, similar to Guzzlord's area, could be that the Ultimate Weapon was fired.

Unsure of Hoopa's entire role but it's the one responsible for summoning the new Mega Pokemon from other realities.

Speaking of which, I only know 9 of the new Megas (excluding Raichu) and I'm unsure if there's more but the list is
>Kingler (Water)
>Sunflora (Grass/Fire)
>Flygon (Ground/Dragon)
>Grumpig (Psychic/Dark)
>Mismagius (Ghost/Fairy)
>Cryogonal (Ice/Rock)
>Toucannon (Fire/Flying)
>Toxtricity (Electric/Poison)
>Dudunsparce (Normal)

That's all I know for now, I'll keep things updated if possible.