Affiliate links might be a good idea in general, adding a partner tag to all links to Amazon for example. I'm sure Amazon doesn't mind, and it doesn't matter to the user, their prices are the same, though clearly stating it is a good idea. For the large retailers that get a lot of traffic and aren't too picky in signups, that could work, but hinges on you getting a lot of traffic that ends up in clicks to shopping related sites.
Unfortunately, I don't think there an ad network to do this. Everyone that I've seen that lets you link to a large variety of retailers without needing to sign up with each one is shady at best (and targets shady sites that wouldn't get affiliate status), so they won't work with the privacy-first approach.
I assumed that with GDPR (and now CCPA) there would have been a greater overall need for privacy focused ad companies, but I may have been wrong.
Building a privacy-first ad network would be a good thing with regards to harm reduction. We're not going to "fix" the need for all the sites wanting to monetize with ads, but if they had a less harmful option than helping Google track your every move, that would be progress.
API.
I think the only way to monetize and preserve user privacy is context based ads. The challenge is that there are very few privacy focused ad networks [0].
So either I need to built an ad network that fits my use case, or try to do direct ad sales. An important part of either of those strategies is user traffic, otherwise no one would be interested in advertising anyway. For that reason I have decided that I will focus on getting people to actually use the site and provide user value first. That does mean I will have to cover the costs in the mean time.
Right now, I do have a clearly indicated ad with an Amazon affiliate link that does display for a limited number of relevant shopping terms, but that won't even come close to covering the operational costs at any volume.
[0] https://news.ycombinator.com/item?id=22362517