Would you trust a phone running GNU/Linux with no proprietary drivers?
Having said that, I would love to have a truly open source phone that I could load any bog standard Linux distro and all the drivers have been reviewed by Linus without him ever once feeling the urge to lift the middle finger. I would only be using it for non sensitive voice and text.
I hope this can be eventually reverse-engineered. Pinephone's modem has some progress.
My daily driver, Librem 5, is as close to such device as possible. It runs an FSF-endorsed OS and has hardware kill switches for wireless and mic/camera. Can't recommend it enough.
> with a really big battery
Instead of a really big battery, I take a couple of backup batteries with me. Replacing the battery takes 30 seconds.
See, I think you can.