There is a thread that was posted by the YouTube Community Manager on the day of the update to share they were "excited" about this new update and touched on some features.
Here is the link to the full thread: https://productforums.google.com/forum/#!topic/youtube/1fMhVozi9Lg
After many many comments and responsed (all are negative) the CM has responded with the following:
"We confirmed that the new version of Android TV isn't compatible with brand accounts for the moment. Here’s more info on how to troubleshoot account login issues. "
Here is the link to the actual comment in the thread: https://productforums.google.com/d/msg/youtube/1fMhVozi9Lg/C3SJ089kAQAJ
I am quite surprised, with such a vague response and basically a slap in the face routing us to the KB which just tells us that it does NOT support Brand accounts.
However she does hint that it is FOR THE MOMENT, so hopefully they had this on the road map already or are listening to all the hate and making changes.
As a Top Contributor for Cast, Home, and other products, I am in these forums a lot and watching for updates. I also will have the chance to meet with the team in Nov at the TC Summit.
Using these help forums is really the best way (other than submitting feedback) to let us be heard and hopefully spark some changes to occur.
This at least shows that they are reading what we are saying so lets hope for the best.
However I am just as disappointed with how this rollout was done.
I have already reverted back to the previous version.
You can as well using these steps: Settings > Apps > YouTube > Uninstall updates
Edit: Below is another very large ongoing thread where a Top Contributor has confirmed this has been escalated.
https://productforums.google.com/forum/#!topic/youtube/kkbMUWQWVnc;context-place=forum/youtube
Edit2: I have also reached out to AndroidPolice, 9to5Google, and AndroidTV.news
None of them had this covered yet and I was surprised especially with the huge backlash. Maybe some more coverage can help our case.
Edit3: Android Police Article:
Edit4: 9to5Google Article:
I don't know if this applies to everyone. I don't use much data, so I use my phone's hotspot for internet. For whatever reason a few months ago, Google released an update that wouldn't allow casting and hotspot from the same device.
Fortunately, the newest version of Google Play services allows this to happen again. The original issue can be found here. Here's the link to the newest apk for Google Play services, since the beta isn't on the Play Store yet.