alt Hacker NewsI really liked silence. I stopped using it when f-droid said the source code was no longer available. Fossify messages is the best replacement I've found.
(I dont bother with encrypted messenging apps. I prefer to assume that anything I do on my phone is doubleplus unprivate. If I want privacy, I head over to my computer.)
GrapheneOS is more well-roundedly private than any desktop OS.
Competition is Qubes but that has usability issues and does not have good hardware security.