Throwing in my anecdotal experience.

I noticed something very similar. About 25% of one-on-one conversations are now in Signal. Another 25% are in iMessage, which is a very easy sell for iOS users.

I've had a terrible time with group chats. One large chat is occurring in iMessage (very poor experience). Another large chat is occurring in Discord, which has been fantastic, but it changes the dynamic and caused a few friends to ghost (the onboarding to Discord is harder for newcomers vs. iMessage, WhatsApp or Signal IMO).