Before you open a menu, check two things. First, that your broadband gives you a public IPv4 address – many full‑fibre and 4G/5G providers use CGNAT, and then no port forward can work. Second, that there is only one router doing NAT: an ISP hub with a mesh system behind it is a double NAT, and the forward has to be set on the right box.
None of the BT, Sky or Virgin Media hubs can update a custom dynamic DNS name, so each guide shows where to run the updater instead. The CGNAT check and the open port checker tell you whether it worked.
