Sorry for the huge delay! I ended up reverting to 2019.x months ago, mostly because URP ShaderGraph performance in 2020.3 was much worse than 2019.x. Right now everything is working for me except for Opaque Texture (if I enable that, MSAA dies) but I'm not using it so I've found my balance. Reflective edges might always be a problem with MSAA I fear, it's still a rather quick AA method after all. I will make more tests with Opaque Texture and later 2020.x versions in a couple months probably.