Apps like Threema OnPrem. Self-Hosted

Here are some great alternatives to Threema OnPrem. Self-Hosted by Threema GmbH :
Speek! - Secure Messenger
Speek! - Secure Messenger
★4.2
Element - Secure Messenger
Element - Secure Messenger
★3.3
MyChat: messenger for office
MyChat: messenger for office
★3.7
StealthTalk: Private Messenger
StealthTalk: Private Messenger
★4.1
Rocket.Chat
Rocket.Chat
★4.2
Criptoo
Criptoo
★3.5
Rocket.Chat Experimental
Rocket.Chat Experimental
★4.0
Mejhool: Decentralised
Mejhool: Decentralised
★3.9
NapoleoN Chat
NapoleoN Chat
★4.4
Whisper MSG
Whisper MSG
★4.0
BBM Enterprise
BBM Enterprise
★3.3
Hide Messages - Private SMS
Hide Messages - Private SMS
★4.4
Messages - Private SMS Vault
Messages - Private SMS Vault
★4.0
Confide - secure messenger
Confide - secure messenger
★4.4
Brax.Me - Private Communities
Brax.Me - Private Communities
★4.5
IMBox.me - Work messaging
IMBox.me - Work messaging
★3.5