Messenger Comparison Table

This is not intended to be an extremely comprehensive list, but enough to get a grasp on the situation.

DivestOS includes Silence, a SMS only fork of Signal, it allows sending encrypted SMS messages to other users of Silence. It is not however recommended for use as your primary messaging client, and is there more as a fallback. The only client for now that we recommend is Conversations, a top notch XMPP client, fully supports the OMEMO XEP, is easy on the battery, and doesn't force you into a walled garden. It is not the easiest thing getting your friends and family to switch apps, so at the very least any apps with end-to-end encryption support should always be preferred over apps without.

As noted below the Signal protocol (double ratchet) is the current gold standard for end-to-end asynchronous messaging encryption.

NameFOSS ClientNon-Free DependenciesFOSS ServerProtocolFederatedDecentralizedEncryptionEncrypted by DefaultBattery DrainData UsageDesktop ClientFile SharingVoice CallingVideo Calling
ConversationsGPLv3NoYesXMPPYesYesTLS + OMEMO (Double Ratchet) E2ETo contacts with OMEMOMinimalMinimalYesYesYesYes
Element/RiotApacheNoYesMatrixYesYesTLS + Olm (Double Ratchet) E2ENot yet??YesYesYesYes
SignalGPLv3Yes, GMSYesCustomNoNoTLS + Signal E2ETo contacts with Signal??YesYesYesYes
Jami/RingGPLv3NoYesCustomN/AYesTLS + SRTP + Custom E2EYesHigh?YesYesYesYes
BriarGPLv3NoN/ACustomN/AYesCustom E2EYesHigh?NoBasicNoNo
SilenceGPLv3NoN/ASMSYesYesSignal E2ETo contacts with SilenceMinimalMinimalNoBasicNoNo
XabberGPLv3NoYesXMPPYesNoTLS + OTR E2ENoLowLowYesYesNoNo
TelegramGPLv2YesNoCustomNoNoCustom E2ENo??YesYesYesYes
KontalkGPLv3NoYesXMPPYesYesTLS + OpenPGP E2EYes??YesYesNoNo
Delta ChatGPLv3NoYesE-MailYesYesTLS + OpenPGP E2ETo contacts with AutoCryptLowMinimalYesYesNoNo
WireGPLv3YesYesCustomNoNoCustom E2EYes??YesYesYesYes
ThreemaAGPLv3YesNoCustomNoNoCustom E2EYes??WebYesYesYes
WhatsAppNoYesNoCustomNoNoTLS + Signal E2EYes??WebYesYesYes
Google AlloNoYesNoCustomNoNoTLS + Signal E2ENo??NoYesNoNo
Facebook MessengerNoYesNoCustomNoNoTLS + Signal E2ENo??WebYesYesYes
Google HangoutsNoYesNoCustomNoNoTLSNo??WebYesYesYes