Assuming, you want to have access from the public internet to port 443 of your RUT (running own web server there ?), you can achieve this using a VPN (wireguard recommended) via intermediate server, having fixed public IP. This can be a very cheap, small VPS. I have one for 2.5E/month.
Usually, it is a good idea simply to ask for a solution for a problem, without "forcing" a specific method.