Interesting post by Cloudflare on detecting #CGNAT as well as the performance and availability impacts to users behind it: blog.cloudflare.com/detecting-…

This re-enforces the importance for both:
1) content providers to dual-stack sites (so that #IPv6 end-users can bypass CGNAT)
2) the importance for networks to deploy IPv6 alongside CGNAT so that only a shrinking subset of traffic needs to go through CGNAT

Of particular concern is the concentration of CGNAT in the developing world, creating even more risk of a multi-tier Internet with an IPv6-centric modern internet but with other parts of the world being stuck in the past with IPv4 CGNAT.

One IP address, many users: Detecting CGNAT to reduce collateral effects

IPv4 scarcity drives widespread use of Carrier-Grade Network Address Translation, a practice in ISPs and mobile networks that places many users behind each IP address, along with their collected activity and volumes of traffic.

^{The Cloudflare Blog}