Ask HN: What charitable efforts make good use of technical skills?

A post I read a while back about an effort to equip an island with a working GSM network using open-source software (https://babyis60.wordpress.com/2010/02/25/the-island-phone-system-adventure/, similar effort https://arstechnica.com/information-technology/2014/02/cellulars-open-source-future-is-latched-to-tallest-tree-in-the-village/) piqued my interest and got me thinking about similar opportunities. Does anyone know if there are any volunteering opportunities doing network / infrastructure building in developing countries? I did my Master's in EE + telecomms.

Looking a bit closer to home, I should probably take a look at Code Club – a colleague had good things to say about it. I was hoping to find something which might (selfishly, perhaps) satisfy my sense of adventure too, however...