Out of all of those, only Instagram is on the list (or I have heard has complied despite not being on it).

You seem to be confusing messaging software and social media ?

Do (the others than Instagram) have an algorithmic feed, or (effectively) do not work without making an account ?

I guess that there's also Discord (that isn't on the list but has still complied) that is in an awkward in-between ?

(IMHO both Instagram and Discord ought to be banned anyway, for everyone, because they're deep web platforms that are owned by Meta/Tencent, and are therefore a threat to the open web and liberal democracy.)