Seems like i was reading a thread about people not getting HBO max on the firestick. You can get HBO Max on firestick very easily. Since it is android based you can sideload HBO Max. It is similar to the way you download Kodi if any of you are familiar with that. I will post a link to a site that gives easy instructions.
I tried the link you provided but got to the Downloader portion and said the website given is not permitted. I went to YouTube and found this work-around from September (the one you linked was in May) - it seems to have worked. I'm logged in on my TV - that's more than I've ever had before. Just seems to e running an Google app on my TV is all (well, on my Firestick).
If it crashes and burns, I'll be sure to come back and update.