If you don’t see the Block option, try these steps:
Open a channel that shows a list of articles, then tap the ... menu (the option may not appear everywhere).
If the publisher is set to See Less, remove See Less first:
Tap ... → Remove from See Less, then check ... again for Block [Publisher Name].
Still not seeing it?
Go to Profile (bottom right) → under Follow / See Less tap See Less, and remove the publisher there.
Then return to the article list and try the ... menu again.