[throwaway675309]

"The other idea I have toyed with, coming from professional ML experience - was to build my own generative model and use it to create my own art assets. Here I wonder how the copyright rules would work - would the assets I train on be subjected to copyright?"

Unless you're training on assets available in the public domain, any generated output from your "custom model" would have the same potential copyright issues as midjourney, stable diffusion, etc. What exactly are you confused about?

[__loam]

I think programmers also often confuse "public domain" with "publicly accessible on the internet"