Changing to orus-io/elm-spa won’t make this situation any easier. The issue is how GH Pages are hosted. You can change your site around to include that nested routing, but it’s still a pain compared to hosting somewhere else.
Not to dissuade you from trying orus-io/elm-spa or Elm Land, both are solid options.
I think, I’ll try one which is easy to use and attractive enough, just for learning purpose. So, maybe Ryan’s elm-spa on mac OS or Elm Land on Ubuntu Linux, both with Netlify.