Free Software

I understand that many people have been burned by large companies pushing proprietary software but for me I would not buy a cell phone from a non profit. The problem with non profits is they don't have money or resources and they often lack the motivation and organization of a company.

Just my 2 cents

If you are still interested, I have the original PinePhone. I've been using it as my only phone for around 2 years. It's slow (I think the hardware is from 2010?) and not very good in general, but I don't want to use a proprietary operating system, so I'm stuck with it.

PinePhone Pro is way faster, has better cameras, but it's still not gonna be as fast as a modern phone (I think it uses 2016 hardware?). It has worse batter life than the original PinePhone, unless you add some proprietary firmware (https://xnux.eu/log/083.html - note that this is an old post) - then it's supposed to be similar to the original. The original PinePhone lasts a day if you don't use it much. If you use it, it will probably only last a few hours. If you buy the keyboard case with builtin battery, it will have 3x as much power, but the case is very thick (https://web.archive.org/web/20230523083341/https://phal.io/tech/pinephone-keyboard-review). But there is at least one other extended battery case that you can buy or 3D print.

A true Linux phone that can be flashed with Mobian (mobile Debian) or any other Linux distro.

PinePhones need custom kernel patches. For PinePhone Pro a lot of them have been upstreamed to the Linux kernel, but if you want everything to work, it might still require a custom kernel. So I'm not sure what experience you will get out of a normal distro (I suspect some things might not work). But you can install Mobian, postmarketOS, Manjaro ARM and more. Those are the mobile distros that most people use.

Note that Mobian has 2 proprietary firmware packages (https://packages.mobian.org), so technically it's not a fully free distro. They are probably necessary for WiFi and Bluetooth to work. I don't know how free other distros are, but I doubt that the other ones that I've mentioned are any better.

possible dead development of Mobian

Pine64 only develops the hardware and all software is developed by the community or Purism (the company that makes Librem 5). Mobian isn't dying, the problem is with the kernel for the original PinePhone (which is maintained only by the community). But there is nothing to worry about for the PinePhone Pro according to Mobian devs: https://blog.mobian.org/posts/2023/09/30/paperweight-dilemma/

good gps navigation

I don't use it much, but last I checked mine, it was off by around 1km. PinePhone Pro uses the same modem, so I don't know if it's better. But maybe things got better if you use newer versions of software.

I think if you buy it, it should be with the expectation that you are buying a toy to play around with. Because it's hard to say if it will work out for you. I've heard that PinePhone Pro has issues with call audio quality. In my PinePhone, modem sometimes doesn't wake up from suspend, so I have a script to reset it. So sometimes you will have to use workarounds to improve things. If you don't use a stable distro, some things might also break from time to time.

Also, the modem runs proprietary firmware, which has some vulnerability that can be exploited locally. There is a libre replacement for one of those parts of the firmware (the rest will still be proprietary), but it's not shipped with the phone, so you will have to flash it yourself: https://github.com/the-modem-distro/pinephone_modem_sdk

Software is another topic. You probably won't be able to use Signal for example (requires an Android app), unless you use Waydroid, which lets you run Android apps.