It's taken me a while but I've finally decided to put my Raspberry Pi 4 to good use and managed to successfully set up a NextcloudPi instance, using the image on the ownyourbits website. Everything seems to be working fine, including being able to access it from outside my network, via the FreeDNS domain I set up.
The only problem I have is that to access my cloud from outside my network, I let the settings in NextcloudPi set up the port forwarding automatically on my ZyXEL VMG8924-B10A. For this to happen, I had to enable UPnP but if I then disable it, as recommended, the ports are closed and I am unable to access the cloud from outside my network.
Having delved into the router settings, I find that Nextcloud automatically sets up the port forwarding under the UPnP tab in Home Networking and not in the Port Forwarding tab in NAT. This is wrong, isn't it (?) so should I delete whatever is in the UPnP tab and manually set up port forwarding? If this is the case, I'd appreciate some guidance in setting up the port forwarding as I'm not 100% sure what I should do. Ta.