Suttree was the first book CM started on and Sut was originally a Dedalus tortured artist type character referred to as “The Poet”.
Obviously that doesn’t mean he is a writer/artist in the final form of the book though there are enough hints along the way. And towards the end direct textual evidence:
“I said that I would take my own part against the slander of oblivion and against the monstrous facelessness of it and that I would stand a stone in the very void where all would read my name. Of that vanity I recant all.”