Open free messenger?

Question

Messengers

I need a free messenger server which I could deploy at my place
Preferably with the possibility of open registration, and not only through the admin

Platforms: Win, Android (preferably IOS, Web)

Are there any?

Answer 1

Jabber, the choice of servers is simply huge

Answer 2

free messenger

https://conversations.im/

the server of which I could deploy at my place

https://prosody.im/

Answer 3

MyChat. There is everything you need, up to 20 connections for free, if more - you need to buy a license. It is deployed on its server in 2 minutes, nothing needs to be configured.

Answer 4

Requirements: Android, Windows NT, GNU/Linux, iOS, Mac OS X:
* Signal
* Telegram ( +web )
* Session Messager (Signal fork)
* Riot.im (synonymous with Element.io)
* Wire ( +web )
* Jabber
* Jitsi (not updated for a long time)
not meeting the requirements:
* Pidgin (Windows NT, GNU/Linux, Mac OS X)
* VK Desktop ( https://vk.com/messenger ( probably Chromium ; Windows NT; web )
* VK Desktop ( Electron ; Windows NT, GNU/Linux, Mac OS X; web )
* BitMessage (Windows NT, GNU/Linux, Mac OS X)
*Increased cross-platform requirements were convenient for displaying supported platforms
. I mentioned different messengers. It's worth thinking about the nature of the question: an all-in-one style open messenger (a bunch of social networks/protocols, like an email client in relation to mail), an open messenger for a proprietary technology (just a nice API wrapper), or an open messenger for an open (or private) technology).