As far as "protocol" with AA meetings, why don't you sit in on a few of them yourself? This is the perfect time since there are so many on Zoom. Just find an "Open" meeting: that means anyone is welcome to attend and you don't need to say why you're there. You don't have to be an alcoholic. You can even leave your camera and mic turned off, and use anonymous. "Just listening," is a valid reply always. Open meetings are basically like a church or Sunday School meeting - everyone is welcome and there is a certain feel to each one.
He can go to any meeting. Again, it's like Sunday School. Come and go where you feel comfortable. He may have lots of friends in that meeting. It's no different than any other social gathering where an Ex might be allowed to be - a bar, a party, church, work, etc. I wouldn't read too much into it.
Yet.
