Of course that is described in the alternatives
If you are behind CGNAT, so do not have a public IPv4 address and do not have a public IPv6 address (check with: ifstatus wan6) or using IPv6 is not applicable then you have to involve a (commercial) third party to get a public IP address.
This can be a VPN provider which supports port forwarding (e.g. ProtonVPN), or you can rent a Virtual Private Server ( I have an Oracle VPS which can be had for free, see at the bottom of this guide), or use things like Netbird, Zerotier, Cloudflared, Tailscale, ngrok, pinggy or tunnelmole and there are more, I have setup Netbird on several OpenWRT and Windows and Linux clients and it works well, see my notes about setting up Netbird on OpenWRT and the Netbird support thread.