Cross-platform VPN without white IP. Similar to Hamachi etc?

Question

VPN

The task is to combine budget with a dozen PCs, OS WIn7, 10, Ubuntu, Centos. At the moment, several computers are connected via hamachi as a temporary solution. Are there cross-platform analogues of Hamachi? Most importantly, there is no white IP, NAT is everywhere, the ass of the world. There is almost no budget for this solution.

Answer 1

Buy any VPS/VDS and install an OpenVPN server there.
Or ready-made VPN hosting.
You need at least 1 static white address for the server.
NAT is not a problem - the port can be forwarded.

Answer 2

Extra-budgetary: connect a static IP service at the provider's home (at my provider it is +20 rubles per month to the monthly fee), flash it into the openwrt router and install an openvpn server there.
Budget: buy a VPS (about 100-150 rubles per month), set up an openvpn server there.

Answer 3

One white IP will still be needed - for the conditional network center. Conditional leaves themselves actively connect (they do not need a white IP) To connect, you can use IPSec - strongswan for centos and bubunta, a built-in client (it has IPSec support, at least in WinX for sure) - for Windows.