Some of my rambling insight on the topic..

In my experience, back before I became vax-disabled, I used go on 5-10 mile hiking trips weekly and do a bunch of kayaking, like almost every other day. I tried lots of offline map options, as I usually was stomping around no-cell signal parts of Southern Illinois' Shawnee National Forest and it's River to River Trail.

Google Maps, even once they started allowing you to cache a small area of map tiles offline, was mostly useless without a mobile data signal. It frequently didn't work without a signal at all, even after smashing through all the settings to disable the tons of shopping and advertisement crap squeezed into it that help kill the app when there is no signal.

It has been a couple years and there seems to be more options now, but I tried many offline map apps. I ended using this, Polaris GPS (GPlayStore) and continue to, although there may be better options now. It has a clunky interface that takes a bit to figure out, but works, works offline, records trails, and allows downloading offline tiles from several providers free.

I found several solar panels (on a budget), including my 16.5 inch (42 cm) square 30 Watt solar panel (EBay listing of same model with specs), to be largely inadequate for...charging a phone, rather on real use on the trail or river. This wasn't the only one to push me into solar pessimism, though.

Hopefully, solar panels are getting better, slowly, but their usefulness is frequently overstated and they are barely a trickle of power, even then, mostly only when perfectly directly hit by the sun from a clear sky. At least that is my experience.

I played with downloading copies of Wikipedia before, so I could host them on a dark-network. I wanted to put a high power Wifi antenna on a tower in the middle of town and provide a free non-Internet connected "Community" network and try to provide as many free downloads and web services I could, as I was somewhat versed in administrating servers and webhosting. If it worked, I had hopes to convince others to put up antennas and to connect them all together, tunneled through the Internet (but not allowing access to it). No matter your big fancy high-gain parabolic or omni-directional antenna, high power, but legal, access point, on a very tall pole...even the slower (ie a,b,g not N) Wifi's usable range is abysmal, at a couple blocks tops, even with line of sight.

Wiki provides up-to-date snapshots of itself and tries to encourage you to do so with lots of documentation. I was just installing a Media Wiki server and importing the data. I also tried converting them the page to all static HTML pages, if I recall correctly. The Wiki snapshots are HUGE, but they give nice options for including just relevant-to-you subsections of content. Setting up all the server stuff was a super big pain. This Kiwix app looks like it may make it easy.