I'm pretty sure this is fake. Thomas did say the house one was fake.
And I think this is from an episode that I forgot which one it is. Gorizilla?
I know I've given evidence that the lair is not in the mansion, but the lair could not be in the pic. He could be transported from there and the window thing is just an obsession of his. I personally think the window could be just a design that is throughout the building wherever it is.
Also, just because it's on the security cams, doesn't mean it's in the house. You can put the camera else where and connect it to the controls in his office. I have CCTV at my house and you don't have to access it by being in the house, but that's kinda different.
I have no idea where this spoiler is from, so I can't confirm it. I would agree with the Luka and Troublemaker thing. If that's true, then Mari's gonna have major heart trouble in this episode! Her crush getting revealed, Chat being Adrien is disguise whilst she probably goes after Troublemaker to save Luka... paradise for the fandom!
French Miraculers, put this on your calendar: 17th June, 9:30 (local time), Troublemaker.
Bug out!