Haven’t really tinkered with anything similar to be honest, but it should be doable. Figure out your software stack, find the lowest power consuming platform you can afford with enough performance to meet your needs, then power it with whatever green energy you can get. There are many commercial solutions for solar+battery combination.

My approach would be a raspberry pi, a power bank and a usb solar panel, I’m curious what kind of experience it would provide.

Screw M.2, I want to use my enterprise grade 7TB U.2 Kioxia drive in my 50 bucks Chinese phone, I just can’t live without it!