- Make sure flag opera://flags/#partner-bookmarks-opt-out is enabled
- Go to opera:settings
- Disable 'Receive promoted Speed Dials and Bookmarks'
As of Opera 57.0, the description seems to switch the meaning of Enable/Disable:
Partner bookmarks opt-out option
Option which allows opting-out from receiving new partner bookmarks. – Mac, Windows, Linux
But the default is
[E], meaning everyone is opted out by default which seems impossible to me... is the wording of this option switched around to the opposite of the actual setting?