Ulysses parallels The Odyssey, which is also a father and son story. I understand how those books are connected. I'm not sure that I understand how GR is a post-modernist retelling of either. Seems like I'm missing something so I'd love to understand in what way GR is related to either.

Perhaps I snuck in a bit of a hot take I had when doing my thesis ;) I find that GR’s cadence and vibe follow Ulysses; the psyche deconstruction that occurs alongside physical meandering through mundane locations are so similar (to me) as to be inescapable.

Sure. I think GR was probably heavily influenced by Joyce and Ulysses specifically. I don't think it's a hot take. I just don't know that I personally would characterize it as a re-telling. GR even goes as far as having mixed format story telling (lots of songs/lyrics in GR) which feels a lot like what Joyce was doing with each chapter of Ulysses (but GR is much less extreme there and isn't as obviously experimental with completely different prose styles or text styles). I think there's a reason why they're often compared and considered the Modernist and Post-Modernist books that define each category.