In that case hardware wise you are out of options. With the Librem 5 you get the closest. There you only have the CPU Microcode, Wifi and Bluetooth firmware, and the cellular modem & GNSS firmware.
Software wise you have quite a few options, albeit few are usable as daily drivers.
- Android drops out because it requires hardware with proprietary HAL. You would have to rewrite huge parts of the OS so that it runs without them.
- Postmarket OS is your best bet for a somewhat usable experience
- Many open source systems run, but calls are difficult to setup and partly unreliable.
- Pure OS should fit your goal best, Mobian second.
With a Droid 4 and Maemo Leste you can also get quite close but have no camera.




Yes tthats pretty much the closest you can get to fully open source today. I have a number of devices I use: A Pixel 5 with Graphene because the modern world relies to much on Android Apps, also used as hotspot, a Nokia N9 for reading and light browsing, occasional navigation a Nokia N900 with Maemo Leste for secure administrative work.
We also have Sailfish devices in the house