Recently after trying to troubleshoot why port forwarding wasn’t working for me I found out my provider spectrum uses CGNAT and when I called to ask about a static IP they said that wasn’t an option. And they said I provided my own modem that I can setup my own static IP. At least to me this doesn’t sound right but I couldn’t find anything exact and wanted to see if this was true or is it best to follow the other methods of port forwarding such as zero tier or using a vpn with port forwarding.
Charter has been quietly rolling out MAP-T. It’s a little different than CGNAT but still involves multiple customers sharing an IPv4 address. However the customers are sharing a standard public address not sharing in the 100.x.x.x range. https://pc.nanog.org/static/published/meetings/NANOG71/1452/20171004_Gottlieb_Mapping_Of_Address_v1.pdf
You will see other ISPs worldwide rolling out CGNAT or MAP-T as well. They are all out of IPv4 addresses or close.
As you say you can do VPN based port forwarding. Wireguard / Tailscale work fine behind MAP-T. Or, just use standard IPv6.
