edit: How do you like extensions to notify of new features? I've seen some do a new tab popup post-install, some just add them and you discover them like DDG, and I'm sure a few have added new features I'll never know about because they're disabled by default. I've always found the new tab way annoying, and I've been slightly less annoyed by just adding the feature with a way to disable.
No notifications at all.
Yes, I understand that it is a conflict of interest between me and whoever writes software.
Optionally, notification in some central standard system of notifications that people hating notifications can silence (not sure is such system existing - if it exists I silenced it long time ago). This would work fine as notifications-haters can disable them and vast majority of people will continue to get them.
So if I'm understanding correctly, you'd be fine with DDG's update if it was just the icon being added to the field (making an assumption here that the icon is how you activate the feature like a password manager), but by adding the ad/onboarding/whatever popup they went too far.
That's a fair criticism! At first, I was taking your stance as it was a terrible wrong that they added another privacy feature in general.