Thank you again for this great post!
I’m a little skeptical about Manjaro on the ZOTAC. I used it for quite some time on a PC but it was always just a matter of time until it broke due to version conflicts. Developers for AUR packagages assume that you’re using the main Arch repo. So when you use the Manjaro repo, which is always a few weeks behind the official Arch one, the AUR updates break pretty regularly. Though you probably don’t want to use the AUR on a handheld anyway.
First there is a fork of Organic Maps, which is called CoMaps. If I understood it correctly, the development on Organic Maps nearly halted for some reason regarding the company that owns it. CoMaps now wants to pick it up again.
Also for navigation I use Magic Earth. It uses OSM data but is not FOSS itself, which is unfortunate. But it offers traffic data which is crucial for good arrival time estimation or avoiding traffic jams.