Some people are reporting seeing a new share sheet in the YouTube app. The new share sheet is visually similar to the current one, which allows sending video links via all supported apps on the phone and also includes other options like Copy Link, Bluetooth, and Nearby Share.
The new share sheet, however, is not displaying all the options to every user. Some can see the non-app options, while others have spotted a few of the apps.
It looks like the new share sheet is part of some server-side updates, as the regression appears randomly across multiple recent versions of the YouTube app.
Users who rely on a functional sharing experience can download the older version of the app to see if that fixes the problem.
In case the new share sheet is nothing but a bug, it is expected to be fixed soon.