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

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.