Opera GX simply shows us the games that have gone free.
I just simply clicked on igdb.com instead of the picture itself, it then shows which platform the game is available. It's actually free on Steam, App Store and Google Play Store, but still paid on everywhere else. Which I don't know why though because when I click on it, it takes me to itch.io to get it for free, but when I get there, it is still a paid game.
It was free for a limited time, simply. Like Steam : now, it's become paid, because was free for limited time, too. https://store.steampowered.com/app/435120/Rusty_Lake_Hotel/