There's another way to check for CGNAT. Go to one of those sites that tells you your public IP like: https://www.whatismyip.com
Now open a command window and do a traceroute to that address.
tracert www.xxx.yyy.zzz
If the traceroute completes in one hop, you do not have CGNAT. If it's 2 hops, the first one is your CGNAT address and the 2nd is your shared public IP.