Are there any highly customizable desktop messengers either cross-platform (maybe even a web app) or for mac?<p>Right now I use Signal which is great but it's missing a lot of features I'd like, many of which are so specific to me it wouldn't even make sense to contribute them via PR. I want to be able to transform the messages directly, add new buttons, toolbars, etc.<p>I'm looking for a kind of chrome-extensions-for-messenger type thing, ideally not tied up with some kind of social media, or ad-network, or gaming, or with a bunch of business features (like Slack etc.). Just a vanilla, extensible, desktop messenger.<p>If worse comes to worst I could whip one up for me and my comrades but maybe y'all have a link that could save me some time.
Mattermost might be too similar to Slack. But it's open source and so are oft of the extensions, e.g. you can self-host and write your own bots. There's a "bridge" to talk to IRC, XMPP, Slack <a href="https://about.mattermost.com/" rel="nofollow">https://about.mattermost.com/</a> <a href="https://github.com/mattermost/mattermost-server" rel="nofollow">https://github.com/mattermost/mattermost-server</a> <a href="https://about.mattermost.com/community-applications/" rel="nofollow">https://about.mattermost.com/community-applications/</a>