YouTube TV and Disney have been fighting over royalties. It led to all Disney-owned channels disappearing from YouTube TV for a while. They’ve now settled the dispute with a new multi-year deal, so all the channels are back. However, local ABC stations may take a while since they're rolling out city by city. There's more.
Disney and YouTube have made up
It's unclear how exactly it happened, given that Disney didn't seem to be interested in making concessions. But YouTube TV and Disney have settled their issues. Returning channels include all the Entertainment and Sports Programming Networks (ESPN), ABC, FX, Nat Geo, and Disney Channel.

Subscribers now also get the new standalone streaming service, ESPN Unlimited, at no extra cost. ESPN Unlimited is ESPN’s new all-in-one sports streaming plan that combines every ESPN channel with ESPN+. That's a lot of ESPN's in a sentence, but you get the point.
It's the full package, including the regular ESPN channels and the addition of Conference networks (SEC Network, ACC Network), ESPN on ABC, along with exclusive games and originals.
You also get ESPN3 and the extra streaming-only feeds, SECN+ and ACCNX, as well as big league games, such as NFL, NBA, NHL, MLB, WWE, college football, tennis majors, golf, and all ESPN talk shows. Usually, it costs $30 monthly and $300 yearly.
You can still redeem YouTube TV credits
Disney made the partnership announcement on their website. A major loss was sitting in the middle of this whole fight if they hadn't agreed. Sports is the backbone of live TV streaming, and losing ESPN during NFL season is basically asking people to walk out the door. It happened eventually as subscribers had to seek alternative platforms.
Once a subscriber leaves for a competitor, it's hard to get them back. Since YouTube TV paid out credits to millions of people as compensation, the blackout was a direct financial loss and a reputational one. Disney also risked making its most expensive asset look unreliable. Thankfully, the battle is over and everyone is happy.

Some of Disney's channels are being reorganized into genre packages, and YouTube TV will be allowed to offer the Disney+ and Hulu bundle inside certain plans. They’re obviously hinting at expanding, and possibly adding more Disney-owned channels or variants.
That aside, if you lost access during the blackout, you may have gotten the $20 credit as compensation, and you can still redeem it until December 9.
Simply open YouTube TV in a web browser and sign in. Click your profile picture, then go into Settings, and scroll to the Updates section. You should see a message about the Disney dispute explaining that a $20 credit is available.

Select the option to claim it, and YouTube TV will confirm that the credit has been applied to your next bill. If you subscribe through Google Play or another third-party provider, the credit may apply automatically. But it’s still a good idea to check the Updates section for confirmation.