Yeah, amazing what's not easy to find.

I recently found out about the ancient roads in China. These days they are hiking paths. I'm quite used to handling myself alone with a GPS track, I don't want a guide. I found one book that it's not remotely clear if it's got what I want as it's discussing much of China and it's old enough I'm not sure what the mapping info will be like.

For the wiki version, you have https://www.wikivoyage.org

It can be a bit outdated, but then you just update it as you do your research ;)

For Seoul, I think this is an interesting observation:

  Seoul is not a pretty city, at least not by most Western standards of beauty.
  It is a sprawling, haphazard mix with little apparent cohesion beyond a shared culture.

Craig Mod is great for Japan https://craigmod.com/ !

Thx, great read about Yemen from Maciej Cegłowski https://idlewords.com/2014/07/sana_a.htm

For Switzerland, for someone who likes railways, I found this guide (missing from guide.travel) to be quite nice: https://www.seat61.com/train-travel-in-switzerland.htm

While planning the trip, I was annoyed by redditors on r/askswitzerland ending almost all replies by asking folks to download the SBB Mobile app. To my surprise, even though I'm not the kind to install apps (let alone Flutter apps), it was god-sent. So well made (their "design system" is open source: https://github.com/SchweizerischeBundesbahnen/design_system_...). Makes travel up and down the country, from Zürich to Lugano, from Genève to St. Gallen, from Basel to Campocologno, stress-free.

For tourists, TooGoodToGo.com (mystery meals) & SwissTopo (trails) are equally neat.