I have a OnePlus 6T running Android 10 / OxygenOS 10.3.4. The problem I'm about to describe has, I believe, been present since the system upgrade to Android 10.
I started seeing these suggestions on various notifications - mainly from messaging apps; the above is a WhatsApp notification. I don't want them, and didn't have a clue how to turn them off because I didn't know what they were called.
Googling various related things ('suggestions', 'smart notifications', etc.) didn't get me any closer, but I eventually found some article on a feature that'd just debuted called 'Adaptive Notifications'. While it didn't mention the above behaviour explicitly, I figured this must've been it.
Switching them off (temporarily)
Sure enough, when I dug through my settings, found the option under Apps & notifications > Special app access > Adaptive Notifications, and switched it to 'None', these suggestions on notifications disappeared after a few minutes.
However, they periodically reappear after I apply a bunch of Play Store updates - and every time they do reappear, I find that 'Adaptive Notifications' has been re-enabled in my settings.
I'm unsure precisely what updates trigger this, but I'd hazard a guess at it being Play Services.
So, how do I stop this from happening?