Edit: I should have further clarified, which I did below. The kicking team recovered it in the end zone, so there was nothing to advance.

The kicking team recovered the ball in the end zone. Possession doesn't start when it's muffed. It starts when it's recovered.

If the ball is mishandled on the 20 bounces to the 10 and is recovered there and run into the end zone, it is returned to the 10. If recovered in the end zone it is a TD, in another wrinkle, if the receiving team player recovers it in the end zone, it is a safety.

a kicking team that "downs" a punt doesn't get the ball i.e. possession unless it touched an opposing player first. But if no opposing player touched this ball before the kicking team fell on it in the end zone it doesn't sound right to credit them a touchdown. A touchdown inherently means possession and possession by the kicking team on a punt doesn't take place unless the opposing player touches the ball first and then the kicking team recovers.

But they've screwed with the rules so much and the officiating is so horrible that I don't bother watching until maybe the last 2 minutes. Same with NBA. Baseball finally is no longer dealing with that horrible ump Angel Hernandez. There's still a few more to go.

Proper application. Ball was recovered at the 3 and run in. The ball was spotted at the 3

Ball was miffed by the receiving player on the 11, bounced to the 3 where it was recovered and run into the end zone. The ref set the ball in the 3

situation. I was under the impression that the OP had been talking about a situation where the opposing team did not touch the ball.

He is saying it was touched by the receiving team outside the end zone but recovered in the end zone.

...but the catch not successfully completed. It has to be touched by the receiving team for it to be a muff.

Scored 26 points without an offensive touchdown.