I've been a user of Tivo for over 15 years and have over 10 Tivo devices.
Yes, you can log into the HBO Max app if you have the HBO Max subscription via Amazon Prime or Hulu, but you can't get the HBO Max app on a Tivo box, so you are again required to use another 3rd party device (i.e. smart TV, Amazon fire stick, or cast to your TV from a aphone/computer/pad).
This is the same problem with Disney Plus.
You can use TIVO Stream (which I have yet to try), but as far as I understand you can't access the other Tivo Boxes (Bolt/Edge etc) in the house so its truly just another streaming device not intergrated with the other TIVO devices like the Tivo Mini is.
Unfortunately, TIVO's in ability to integrate desired apps (HBO Max - Disney Plus) into the Tivo boxes and not allow Tivo Stream to access other Tivo boxes in the house is likely the death of Tivo....at least for me, because who wants to have two devices on their TV to watch what they want to watch?