Why don't think about zerophone? [[https://wiki.zerophone.org/index.php/Main_Page]]
Their attempt to build free hardware is very interesting, and with some modifications (touchscreen instead of little screen + keyboard) maybe it can work with replicant?
RE: Zerophone - Added by Kurtis Hanna 22 days ago
We have recently been trying to focus exclusively on devices that have free software bootloaders that require no proprietary binary blobs.
Here's someone who tried to put u-boot on the Rasberry Pi Zero: https://ktln2.org/2018/10/28/u-boot-rpi0/
It seems as though the stage 2 bootloader is a binary blob called 'bootcode.bin'. Unless this blob is able to be removed, we likely won't be interested in this device as a potential target for Replicant.