A little over a year ago I was fortunate to make it onto the beta testing team for Beeper. TL;DR Beeper is a unified chat application (i.e. all major chat applications, including SMS, in one app). Beeper recently announced that their basic service is now free https://blog.beeper.com/p/beeper-is-now-free. However, they will be slowly working their way through a wait list. The convenience of this service can’t be understated. Also, encrypted services such as Signal are supported. Just go to https://www.beeper.com/ and click the ‘Get started’ button to join the wait list.
Signal seems to be going in the opposite direction and announced the end of SMS support because of the lack of SMS security https://signal.org/blog/sms-removal-android/
Meanwhile Google is pushing RCS hard https://www.androidcentral.com/google-evolve-android-messages-chat-using-rcs-shelve-allo
Looks like everyone wants SMS to die but there isn’t a consensus on a replacement. So I can see the use for an unified chat app. Not sure about SMS support however.