i want to validate this concept (and will again in the future): do you want a linux pocket computer that is not primarily a smartphone, but could be an alternative/substitute for a smartphone? i.e. not focused on the telephone aspect, but on text/writing/CLI/web.
one idea (librem 5 has this already): pluggable cell modem if you want. alternatively wifi or tether to dumbphone/other smartphone.
@mntmn Right now I see the biggest gaps in open/privacy respecting hardware actually being in the tablet and ereader space. So I might suggest something in the form factor of either the ipad mini, or a smaller 6" ereader device.
You could then further extend the utility of the device by having a pogo pin connector on the back/side, allowing for an attached keyboard or other mods. Anyhow, that's my two cents.