What are the options for connecting to remote workstations between sites?

Question

Computer networks

There are 6 objects connected by PPTP tunnels (Mikrotik router). There was a need for a remote connection to these objects. The choice fell on UltraVNC (free, reliable and only the admin knows the password), but it only works on the local network. After reading the information on how to connect to another local network, machinations in the router are needed (for each PC, a port is opened, which is not good). There is an option with a VPN server, but did not work with it. Who can tell in which direction to dig?

Answer 1

Aside VPN and dig. Connect dots with tunnels and knock on computers by name.
Of course, the subnets on the points must be different from each other.