[draft] How to connect a LibreRouter network to a non-LibreRouter network?

Connecting a LIbreRouter to a non-LibreRouter network needs some thought, as the LIbreRouter and the network that it creates includes by default a set of services that ensure that the network works automatically, like the DHCP, DNS, mesh routing protocols, amongst others.

There are different approaches to it:
1.
2.
3.