After all that, weeks of struggling with an install that wasn’t working, in which I was sure that it must be due to something I was doing wrong, or wasn’t doing or something, it turns out that it wasn’t really me at all. It turns out that this domain was associated somehow with another account that I had that I had deleted (? I still am not sure how this is a thing, but, you know, whatever) and I couldn’t install WP onto until I had confirmed that I was that account holder and this domain was added to my current account. Whew.
So now I wait and check and look and customize and hope that was the end of that.