At least with the kindle, when I bought the ad-supported version because I wanted to save money, I just reset the firmware after unboxing and strictly put the books on via USB. I have no need for the device to be online and never once have been greeted by an ad. In Germany we have "Buchpreisbindung" which pretty much disallows eBooks to be significantly cheaper than physical books, so even with no ads shown, big A still gets their fair share of revenue out of me. I guess for smart phones and similar this is not a feasible approach because they pretty much turn stupid without internet access, but at least rooting on Android puts some leverage back into consumer's hands for now.

I would argue what you just said is also a privilege that one must afford: technical knowledge, or the privilege to have access to resources that will teach it to you.

This is exactly what I have done too. Purchase the ad-supported version for (I think) 40 Euros less and simply never connect to the internet. That was over five years ago and I still don't regret it.

It has one more advantage: the firmware is really outdated. Normally I'd consider this a bad thing, but in case I ever want to root the device, the jail breaks are probably for one specific old version of the software, to which I'd have to upgrade. Not downgrade, if that's even possible.

The base model Pinephone is $150. It's not about price, it's about tolerance.

It's not that hard to buy a relatively cheap phone and put a ROM on it. You will forgo some conveniences, but that's the cost of privacy.