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 CallingMulti-Device SupportOffline Messaging
ConversationsGPLv3NoYesXMPPYesYesTLS + OMEMO (Double Ratchet) E2ETo contacts with OMEMOMinimalMinimalYesYesYesYesYesYes
Element/RiotApacheNoYesMatrixYesYesTLS + Olm (Double Ratchet) E2ENot yet??YesYesYesYesYesYes
SignalGPLv3Yes, GMSYesCustomNoNoTLS + Signal E2ETo contacts with Signal??YesYesYesYesWith PhoneYes
Jami/RingGPLv3NoYesCustomN/AYesTLS + SRTP + Custom E2EYesHigh?YesYesYesYesYesNo
BriarGPLv3NoN/ACustomN/AYesCustom E2EYes??NoBasicNoNoNoNo
SilenceGPLv3NoN/ASMSYesYesSignal E2ETo contacts with SilenceMinimalMinimalNoBasicNoNoNoMaybe?
XabberGPLv3NoYesXMPPYesNoTLS + OTR E2ENoLowLowYesYesNoNoYesYes
TelegramGPLv2YesNoCustomNoNoCustom E2ENo??YesYesYesYesYesYes
KontalkGPLv3NoYesXMPPYesYesTLS + OpenPGP E2EYes??YesYesNoNoYesYes
Delta ChatGPLv3NoYesE-MailYesYesTLS + OpenPGP E2ETo contacts with AutoCryptLowMinimalYesYesNoNoYesYes
WireGPLv3YesYesCustomNoNoCustom E2EYes??YesYesYesYesYesYes
ThreemaAGPLv3YesNoCustomNoNoCustom E2EYes??WebYesYesYesYesYes
WhatsAppNoYesNoCustomNoNoTLS + Signal E2EYes??WebYesYesYesWith PhoneYes
Facebook MessengerNoYesNoCustomNoNoTLS + Signal E2ENo??WebYesYesYesYesYes
Google HangoutsNoYesNoCustomNoNoTLSNo??WebYesYesYesYesYes
SkypeNoYesNoCustomNoNoTLSNo??YesYesYesYesYesYes