Okay, but is there any circumstantial evidence for a writing system that dates earlier than very early cuneiform? /s

I guess, what OP is asking is more of a question of, "have we found any evidence that can support the theoretical existence of a known script existing at a date preceeding our oldest surviving examples of that script?"

I, for one, have no idea how to answer this question.

Because, while yes, the earliest examples we have are not the first examples in existence. There are probably hundreds of thousands of documents, inscriptions, minute changes, etc. that compunded far before the scripts reached the level of development we see in our earliest surviving examples.

But at the same time, by definition, we don't have evidence for the existence of such a script yet.

No serious historian would ever give a terminus post quem for the development of a writing system unless it was created by one guy at a very precise moment in time (such as King Sejong and Hangul). So how do you satisfactorily answer this question for other languages?