I've heard of one of these people, but only because of a single youtube video. The talkshow host therein mentioned something about Cumberbatch having two fan-groups that somehow hate each other. No idea who the other two are. Dua Lipa sounds like "Dual Lips", so I'm guessing Only Fans or porn star.
Among the famous people to put their names to the letter are singers Dua Lipa, Annie Lennox, Paloma Faith, Massive Attack and Primal Scream.
Sooo, she's a singer. Must be rap or something. Now I have to check it out.