Which way to build a VPN to choose for 40 Mikrotik and Keenetic?

Question

VPN

There are 40 remote local networks. At the border of each network there is a Mikrotik RB941-2nD-TC or Keenetic City KN-1510 router. The provider issues white static addresses for all connection points.
You need to build a Site to Site VPN, connecting all local networks.
Which protocol to build a VPN to choose to ensure convenient network administration and sufficient fault tolerance?

PS I do not consider Ipsec, openvpn, pptp with encryption due to insufficiently productive equipment for encryption.

Answer 1

Well, except perhaps l2tp without encryption then.
Although it’s not clear to me how you can build a network on Dishman shit and expect something from it ... But it’s true, my imho

Answer 2

GRE - minimal overhead.

Answer 3

The provider issues white static addresses for all connection points

Is it the provider in the singular? Then it is worth talking with the provider regarding the connection of networks with its capabilities. Moreover, it can also be economically beneficial. For example, quite a long time ago, several sites paid for l2vpn 100Mbps slightly less than for 10Mbps "Internet".