Not really an answer, but too big for a comment:
You have two questions:
- how to set up a LAN/WAN
- which hardware to use to communicate over 10km?
You should also consider whether you want some sort of centralized network, with a server or totally distributed, where everyone’s device an talk to everyone else’s without any centralized architecture.
Also, what happens if someone wanders out of range and comes back? Do they just lose contact, or for instance, if they are gathering data, should that data be synched when they return? If so, you need Delay-tolerant networking – have a look at my answer to this question.
To be honest, I think you need to give us a lot more detail about what this LAN will be doing, for us to be able to give you meaningful help. If you update your question, I am sure that you will get better replies.
Ok, so, from your comment, you are speaking of a Community Network. That helps to know – the more detail in the question, the higher the chance of a meaningful answer.
https://www.nycmesh.net/blog/how/ looks helpful – it basically explains how to do it. I am sure that you can find more if you DuckDuckGo, and reading the experience of someone who has already done it will be extremely helpful. In fact, if you contact them, they might turn out to be very helpful. Hmmm, there’s a good business there for someone, setting up & supporting community networks.
The networking is trivial (unless you want DTN). You can simply Google, or ask on https://superuser.com/ or https://serverfault.com/
You can ask about hardware in BUT, you will have to give a lot of detail regarding distances, the environment (single building, city centre or countryside).
If you need software to administer your network, or for other applications, then ask on https://softwarerecs.stackexchange.com/
You might also want to be aware of https://webmasters.stackexchange.com/
I don’t know if it will make a big difference, but telling us your location & what the network will be used for might bring out some more helpful ideas.
Good luck, and please do come back later and tell us of your experiences.