I like this idea, but I think you should work a bit of history/philosophy into each lesson by explaining why things work the way they do. The students are unlikely to engage with a history of a system they’ve never used before, so starting with that will lose their attention before you’ve even gotten it. Giving them a bit at a time means that they will slowly build a mental model of how *nix works and is built.

OSM for day hikes and Avenza for anything more serious.

Yes, but you have to buy a subscription to Protonmail Bridge which see decrypts the emails for Thunderbird.