Strange , I'm using Att sim on my unlocked Note 20U and Google message app but don't have anyone group messagingYep, I found the same after some digging today. These APN settings are also working for me, for the moment anyway.
https://www.4gapn.com/us/en/att
Crazy that an end user has to do this, right?
Interesting, thanks for your findingsWas having similar issues with my Note20 5G. I was trying to use Google Messages but my Chat features wasn't enabled and said that it wasn't supported. But there was a learn more, after opening that up there was a link to agree to use JIBE from Google and when I agreed the app ran and verified my phone number and opened the enable window and boom it works now.
Even though this not for google chat not register a number hopefully can help someone that runs into it .Yes apparently the Google Messages app was still trying to run with my number through my old phone. So the chat feature need to enabled with the new phone.
Wow that's still a issueI've noticed this happening to me recently as well. I've found that turning off Wifi and WiFi calling fixes this. I'm on ATT so I don't know if it's an ATT thing only in my end.