Comment by petiepooo

We implemented a very similar solution more than five years ago. The NanoPi R3S was not available then, so we used the GL.iNet GL-MT300N-v2 (aka Mango) running OpenWRT as our edge gateways. It's slow and only has two 100Mb ports, but that was never the bottleneck. At that time, I was able to assemble a batch of 10 including cables and power supplies for only $300, which was ridiculously cheap for such a flexible solution. If you need a polished, turnkey solution, by all means check netrinos out. If you have a strong Linux/nftables/wireguard background, this solution is easy to roll on your own.