Signal, Threema and similar "alternatives" to Whatsapp are siloed, walled gardens.
For our #digitalSovereignty, we need to have technology like the #fediverse, that does not depend on the Amazon cloud and can be shutdown by Jeff B. or DJT at their will.
In the case of #instantMessaging, this technology exists since 1999 and is called #Jabber or #XMPP.
A very easy to use app to join that network is #Quicksy (Android, iOS). Why not give it try?