My idea is one step further: selling the device with various ad-blocking and user-selectable tiers of security configuration included. Stop your devices spying on you, detect/notify if you have any infected devices on your network. That kind of thing.

Similarly though, there's limited appeal to those who aren't already capable of setting it up themselves.

I'm still slowly pursuing this because I believe in it, whether it's profitable or not.

Edited to add: Part of what I'm setting up: https://lists.uninvitedactivity.com/DNS/, a vague explainer here: https://news.ycombinator.com/item?id=49990394