OK. So.

I have a Sony Bravia that runs Android. For ages, it simply replicated my You Tube channel on the You Tube app, so all my subscriptions, things I had watched and so on were present the same as on my computer.

Then, all of a sudden, it just ceased to be logged in. Still worked, but was no longer 'my' You Tube.

Eventually, after lots of searching, I discovered that the new version of YT TV on Android TV is now not compatible with 'brand accounts' and you can't log in with one. Why you can do so on a computer but not on the TV entirely eludes me, but there you are.

I find that I have 3 'brand accounts' with Google - news to me as I thought that I had only one account to be honest. I have two businesses which are quite different and so clearly at some point, without my really realising, I have ended up with two accounts and somehow a third one which has the same name as one of the others.

I really do not have much clue what the difference between a brand account and any other account actually is, why I should care or how to change from one to the other.

I sure as heck have no idea why the nature of the account would have the slightest bearing on what devices I can or cannot log in to You Tube with.

I would like to have the same YT on my TV as I have on my phone and my Mac. 

Aside from casting from one of the other devices - which seems an insane work around - can anyone who understands how Google stuff works better than me suggest a way to make the TV work the way it previously did?

Edit for clarity: I cannot log in to YT unless I log the TV itself in with a non 'brand' Google account. Surely I do not need to create YET ANOTHER Google account just to watch the apps on my TV?