They’ll can be used in all the contexts in which they is used by itself, including in reference to multiple people or to a single individual.

Don't mess with Attack on Titan fans

They'll spoil the entire manga.

— Pride (@PridefuISin) December 22, 2020

If someone really wants to see you, they'll find a reason, they'll find a way, and they'll make the effort.

— Fact (@Fact) September 27, 2022

8yo told me last night that "when they're old enough" they'll go by they/them, and I was like "honey you can do that now if you want to." 😂 So they are they/them now, "for two weeks. Just to try it out." 😆❤️

— Oy Geralt (@thekvitcher) September 23, 2022

Did you mean LL?