I switched to ATT Fiber around a year ago (from Spectrum) and I've had no issues thus far. Their provided gateway doesn't properly bridge though, creating a double NAT situation. I worked around this by getting my own ONT and then writing the data from the old gateway to it (S/N, ONT ID, etc.). As for CGNAT, my network has a public facing IP, not a CGNAT'd one.
I switched to ATT Fiber around a year ago (from Spectrum) and I've had no issues thus far. Their provided gateway doesn't properly bridge though, creating a double NAT situation. I worked around this by getting my own ONT and then writing the data from the old gateway to it (S/N, ONT ID, etc.). As for CGNAT, my network has a public facing IP, not a CGNAT'd one.
If you're curious about using your own ONT, here's the guide I used (I believe you'll need a BGW320 originally to use this): https://docs.google.com/document/d/13gucfDOf8X9ptkj5BOg12V0xcqqDZDnvROJpW5CIpJ4/view