Lineage and GrapheneOS have proven that reverse engineering is hard. So I'm wondering why can't we have a project that starts from scratch and build the electronics and the OS? In the same spirit of what Apple did with iPhone+iOS. I'm sorry if I sound naive, I just don't realize how hard it is to design a smartphone.
[1] https://news.ycombinator.com/item?id=45586339
But even for a phone from 2015 there were many models on the market, I don't expect every brands poured that much money in developing a phone. What justifies such a big budget? And what could be a minimal budget for a decent phone?
By decent I mean an average phone: can run most of basic apps, average battery life and pictures quality.
Most drivers, radio devices, kernel, android releases are those you get at the beginning, you can't really change a thing due to them being closed source or just one step above from being a firmware blob with a few kernel hooks and once your contract expires your devices die with it.
We investigated if we could at least maintain the software on our own (so to not tell some telco clients their streaming devices were gonna die after 4 years) but it was a big fat no from the licensees. And reverse engineering what we already had was forbidden by contract.
In other words, if you want yo build a free phone, you need to build a free radio, a free storage solution, thousands of weird DACs, graphic cards, screen controllers, sensors and whatnot. Making sure you're not infringing on some patents. It's like starting from ground-up. And it's expensive.
A possible solution would be to invest into building into a raspberry-pi binary compatible base platform (and take advantage of their already open sourced drivers), but it was 100% economically unfeasible for a 100-200€ device.