Signal as an easy-to-use and probably more secure WA replacement? Sure.
But for #digitalSovereignty we should go for something really free and federated, just like the fediverse. There are various options, of course. Each with pros and cons attached.
(My personal favourite is #Jabber, which exists since 1999 and is extremely easy to use thanks to #Quicksy and its Indian cousin #Prav.)