Pidgin is a chat program which lets you log into accounts on multiple chat networks simultaneously. This means that you can be chatting with friends on XMPP and sitting in an IRC channel at the same time. Pidgin runs on Windows, Linux, and other UNIX-like operating systems.
Official site
Or use https://spectrum.im/ Which is basically a server side Pidgin (uses the same libpurple plugins) and you can connect with any XMPP client.
Or BitlBee (https://www.bitlbee.org/main.php/news.r.html) which is the same thing but as an IRC server (This is what I use)
https://github.com/42wim/matterbridge also matterbridge does the same thing I believe
Somewhat different. Matterbridge makes a connection between one or more chat rooms, while Spectrum2 allows you to connect as a single user to a different network.
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Matrix? It’s all XMPP. Has been available for many years and is pretty stable for small scale use.
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