Spark
spark
XMPP Client
Spark is an Open Source, cross-platform IM client optimized for businesses and organizations. It features built-in support for group chat, telephony integration, and strong security. It also offers a great end-user experience with features like in-line spell checking, group chat room bookmarks, and tabbed conversations.
Java
Linux
macOS
Windows
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partial

Images only.

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Http File Upload Plugin (fileupload) plugin

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complete

Online Meetings (meet) plugin