Another threaded slack alternative I've found enjoyable is Spectrum. (
https://spectrum.chat) They've recently open sourced as well, (
https://github.com/withspectrum/spectrum). Their design is appealing, and I can see a lot of work being done on the platform. Not affiliated or anything, just a fan.
P.S: I'm trying to create a community for "Bored Hackers", and you can check it out here and say hi! (https://spectrum.chat/boredhackers)