How to connect several offices into a single network?

Question

network hardware

Good day to all.
There are several offices (or rather four) in different cities.
The task is to combine them into one network through net.
There are 4 microcomputers. There is an idea to put Linux on them and use them as a router.
There was an idea to connect them via IPSec tunnels, but they "spit" on me and said that this was not a good idea, but they did not advise anything in return.
I know that a lot of cool network specialists "live" here, so please, tell me the best and most stable option for combining them.

Answer 1

Microcomputers ... Install routers, why bother with non-core equipment of unknown performance?