Best Group Messaging App that Isn't iMessage

I'm thinking I'll probably just use Apple's Messages app once they implement RCS, but I'm hoping for some advice on a good group messaging app to use right now. Currently I do most of my messaging through Facebook Messenger and Discord, and both work ok, but there's one thing they don't do that frustrates me. There is no sound queue when a new message arrives in a message thread that you have open. When using iMessage there's an audio queue for that. In Messenger or Discord I often find that once I send a message I'm repeating something someone else just said or asking a question that already got answered because I didn't think to check new messages before hitting send. I can work on getting into the habit of checking before I send, but I would be thrilled if there's a messaging app I can use that has better sound queues.
Also Messenger has this weird bug that sometimes when I send or receive a message it just starts reading messages in my open thread from days ago and won't stop until I close and re-open the app. Not sure what's up with that.