I realize that "f*ck google" is one of the tags for this thread, but I'm going to risk having my head bitten off, and being drummed out of this community. I am going to claim that the best handheld gnu/linux machine for 2017 and the foreseeable future is an Android phone running Termux. Termux allows you to run gnu/linux applications, on an unrooted Android phone, compiled for 64 bit arm. Termux is open source, with an active community. I can run Python 3.6, iPython, sympy, numpy, scipy and astropy. I run it on recent hardware (a Pixel XL), and when that machine is obsolete, it'll be trivial to get newer hardware. If I cared about Google's collection of my data (which I don't), I could just create a throw-away gmail account for it under a phony (no pun intended!) name, and leave it in airplane mode all the time. If I cared about a hardware keyboard, I could run it on a Blackberry phone, or some other Android phone with a keyboard. What currently available handheld gnu/linux machine is better than this?