And consider installing the Amazon Smile Redirect browser extension.

Are you sure Amazon is not using smile as a pricing indicator? I.e., people who want to donate to charity maybe less price-conscious?

That's the reason I've not started using it. Online stores use all kinds of indicators (user agent, OS, number of searches for similar items, etc) to jack up prices when they think they can get away with it, and I suspect this metric is very relevant in that context.

I just donate to EFF and others directly.

Or Project Smile. I realize this has nothing to do with the EFF, it's just a project that should get a lot more press and support.