Cyberdecks are a bit of a hobby on hackaday, of the major issues they face today

*IO often sucks

*operating systems suck

*compute performance sucks

*battery sucks, and explodes

To my knowledge the closest thing we have today is the librephone, its open source, runs Linux, is otherwise phone like with sim comparability. What are you trying to accomplish that you don't want "a phone", privacy/security? GPIO pins? Multiple NICs?