Out of curiosity, how does your setup look for Smartdns?
Did you add the addresses directly to your router's config? I'm using the SmartDns Client app which I manually activate on my MiBox when the wife and I want to watch Disney+. However, I found that Showmax and DSTV Now's apps have difficulties in accessing content using the local DNS addresses. It's a bit of a hit and miss affair, sometimes it works, other times it doesn't.
But it's quick and easy to turn it off via the app before accessing Showmax or DSTV Now, so it's not a huge train smash. The nice thing about the SmartDNS client app is that I don't need to activate my IP via the website each time I power off my router + ONT. The app does it automatically for me.
@Jasondruck - The easiest way to get Disney+ installed on your MiBox without side loading it, is to create a new Google account using a US based VPN. Log in with that account on your MiBox (or add it to your existing one) and then open up the Google Play store. You'll find it there. Just select it and choose install. Done and dusted