If there are some handcrafty people on Pinephone Pro around: try some opensource denoiser like rnnoise. If it works, then it's probably worth the effort to integrate a opensource software VoWifi (using doubango IMS -- even if it's to do VoWifi over LTE), since that will allow you to use the denoiser (and the codec!) of your choice, rather than using whatever Qualcomm has in that quectel module.
In my opensource software VoWifi for Android implementation, I already implemented rnnoise, because I know that the denoiser you get on smartphones vary wildly, and there is a nice "unprocessed" audio source on most smartphones to bypass the vendor denoiser.
I've had various issues with vendor denoiser, going from, no denoising and no silence injection at all, but with AGC, so when I stop speaking the other side hears the noise very well. I've had vendor denoiser eat some very specific pronunciations: my guess is that it was calibrated for CN languages rather than europeans. And then, there is Qualcomm which have various levels of denoiser ("fluence"), which costs more or less, so if OEM is cheap... well denoiser is cheap.
On the rest of the article, despite my love for opensource software, PPP is nowhere near usable for me, so I commend the author for sticking with it so hard. I've tried PPP a bit, but the form factor alone kills me (well my daily driver is smaller than anything you can find.
Camera is really an issue, we really need opensource software processing pipelines -- that'd be slower, but much easier to improve, evolve and customize, and you can do the processing "later" (save only 10 raw frame burst, and process them during the night into merged photos). That's my wish, though sadly I tried doing it and so far failed spectacularly...
> are also getting completely open source firmware, like the Modem itself,
yeah... it isn't. opensourcing the AP of the modem is not very interesting, since you just end up with something as open as a smartphone. The modem's modem is still closed source.
> Texting in SXMO happens through the Linux console, neatly wrapped up in scripts and menus that make it easy. All you need to know, is that the text editor requires one press of the "i" key, before you can start writing.
Uh. That's next level usability... Don't get me wrong, I'm a fan of vim, but uh maybe not on a smartphone. At least that's not a selling point.