And not only Signal themself can pull the plug.
DJT holds the #killSwitch in his hand, by means of his best bro Jeff B.
#WalledGarden is walled Garden. Better use sth. #free and #federated. #Jabber/#XMPP, Jami, Briar, Matrix, Delta, whatever.
The biggest problem is that, on iOS, Apple holds the kill switch. Signal is GPLv3 and requires a CLA that allows them to distribute it via the Apple App Store, but no one else can distribute it.
If Signal or Apple decides to remove their app from the app store in a jurisdiction, every iOS user loses access. In theory, the EU CMA addresses this, but in practice Apple's malicious compliance means it's completely ineffective (unless they start issuing massive fines and make Apple stop).