How to organize access to the network behind Mikrotik without a white IP through another one with a white IP?

Question

Mikrotik

Hello dear!
There are several scattered Mikrotik RouterBoards, with OS version 6.33+ if it matters, connected via PPPoE without white addresses. It is necessary to get to them and to the networks behind them (NAT is raised on them for their networks, respectively). The only possible option that I see is to create channels from them to the same Mikrotik, but with a white address, which is in my house.
In a simple form, the scheme can be depicted as follows (if it is needed here at all):

That's just how to organize it correctly - which channels are better to create and how to get to R2, then to R3, both on the routers themselves and on the devices standing behind any of them?
At the same time, of course, without losing access to your R1 home network and without routing all Internet traffic from R2 and R3 through yourself.

Answer 1

Raise a server on a white VPN server (the same OPENVPN, SSTP Mikrotik), connect Mikrotik after nat to an external one, configure static routing.

Answer 2

l2tp + routing

Answer 3

do it according to the well-known scheme: IPSec + Mikrotik, why doesn't it work?

Answer 4

wiki.mikrotik.com/wiki/Manual:IP/Cloud and vpn server raise