I SOLVED THE PROBLEM!!!
I've been having the same problem as everyone else on this chain, but I solved it. I bought a Five TV and a Chromecast and threw my two Rokus in the garbage. Everything is working as it's supposed to. HBO Max does not go to black ever. Problem solved!
Added bonus: from what I can tell from the internet boards, customer service for both other products are actually responsive and helpful and solve customer's problems for them.