My public IP shows at 213.xxx but if I run a tracert I can see several 10.124 addresses.
Could be both CGNAT and a bad setup on the MIkrotik, I have asked the carrier if they will assign me a public IP address so at least I can rule that out!
The fact that tracert shows some private IPs is not a problem, the ISP may use them inside their network. What is important is whether the address you've got on your router's WAN is a public one or not. If it is a private one or one from the CGNAT range, the outcome is the same, your router cannot act as a server/responder to incoming connections, and since there is NAT, ancient VPN protocols (PPTP) usually do not work.
So what exactly means "my public IP shows at 213.xxx"? If some "whatismyip" web page shows it, it says nothing, as it is the public IP from which your connection has arrived to that web, so it may be some NAT device far away from you; what matters is the IP address on your WAN interface.