Do you want to know how to make this possible with this very router?
Yes, I guess that would be the most convenient way if it is possible for this router. Or maybe buying another router is an option, but then I have to make sure it has SIM card support and port forwarding.
How about allowing incoming connections in another way?
I also thought about using my VPS as a proxy, so my node could initiate a connection with my VPS, and that server would connect with the rest of the world. Of course, in this case the easiest way would be just running a full node on my VPS directly, but as I want a full node and I don't have 400 GB disk on my VPS, I thought about just routing the network traffic through my server.
Using Tor may solve my problem partially, I will try to set up that, but I am still looking for a way to do that also for clearnet connections.