I find just pinning the tab (right-click on tab, select Pin Tab) on Firefox does what I need it to do. I mention this because I suspect many people are unaware the feature exists.

Pinning a tab gives it permanent priority on the left-hand side of the tab list, and elides the title from the tab, so it is just the favicon. It also blocks CTRL-w from closing the tab; you have to actually right-click and either unpin or close the tab. That may sound trivial, but was the biggest problem I had running it in the browser before, it got caught in my periodic tab cleanups accidentally. Now I never accidentally close it.

There is also wee-slack[0], a plug-in for weechat specifically that does more than the IRC gateway

[0] https://github.com/wee-slack/wee-slack

eul.im is a closed-source commercial lightweight chat client launched 6 months ago; the author spent a few months advertising on related discussions until snagging a bit of critical feedback. https://hn.algolia.com/?query=eul.im&sort=byDate&type=commen... https://news.ycombinator.com/item?id=15597468 (apparently it still downloads a 180MB embedded browser https://github.com/eul-im/eul/issues/60)

There is also https://github.com/bkanber/Slackadaisical (no development since initial October appearance) CLI and:

https://news.ycombinator.com/item?id=15597508 >nikisweeting: https://github.com/saenzramiro/rambox [...] https://github.com/meetfranz/franz [...] share one Electron instance for all your chat services