If you read the article, this isn’t a rarest ending like the headline says. There is an ending playing as Lae’zel most players don’t take because it’s a bad ending that obviously ends the story. The ending being talked about is a hacked ending that was maybe an idea at one point to get to the above ending via an alternative path, but wasn’t ultimately implemented. I wouldn’t even call this an ending frankly. It’s more “there’s some game files that can lead to each other if X or Y is marked, but actually can’t because Z being marked cuts that path off”. More of a glitch than anything.
So from the article the Lae’zel ending only happenings if you
Super spoiler don’t think there’s a spoiler text accepted across all instances yet
Accept becoming a mind flayer and some events thereafter and then follow through with Vlaak’ith telling you to kill yourself. This “rare no one’s taken” glitch ending seems to be if you listen to Vlaak’ith, but don’t turn mind flayer you can still take the kill yourself ending if you check the mind flayer box …despite not being mind flayer. Which could only happen through a glitch. So it’s just a you could take this path if you’d checked X box but you didn’t so can’t “ending”. I’m not sure what this article is trying to say honestly as it’s literally just “if you make X choice you could get Y ending, but if you glitch the game to believe you made X choice you could get Y ending” article.