However, they all seem not great and am curious to see what more experienced folks have to say.

It does make me beg the question of why using `global` is seen as such evil but if I do

class Foo:
var: str

@classmethod
def init(cls, val):
cls.var = val

init = Foo.init

That's somehow ok? All you're doing is adding an extra namespace to have to drill down into.