We just use Discord. My daughter is 11 and has been on Discord for a while and uses it to talk to her friends while they are all gaming together, and can use it on her computer, phone, and tablet so she doesn’t have to switch devices just to talk. Granted my daughter does have her own phone number, but she’ll still use discord for her group chats just because of its ease of use and the ability for her and her friends to jump on a call to mine some crafts or ro some blox or whatever it is kids do these days.