Hallå Kitteh
If you're not trying to leave #Slack already, here's some additional incentive:

https://social.heldscal.la/url/545072
Jun 16, 2017 at 6:35amWeb
Show threadHallå KittehJun 16, 2017
#slackalternatives #hprep

https://microca.st/clacke/comment/l11mIRDiQWikamj6hvp1wA has a bunch of discussion, but microca.st is unreliable and currently the cert is months too old, so I'll extract that information.

http://tiptoes.ca/3107-2/ mentions http://ryver.com/ryver-vs-slack/ .
Show threadHallå KittehJun 16, 2017
https://zulip.org/
http://mattermost.org/
https://matrix.org/
http://sdelements.github.io/lets-chat/
https://rocket.chat/
http://buddycloud.com/

XMPP frontends:

http://getkaiwa.com/
https://conversejs.org/
https://www.jsxc.org/
https://jwchat.org/
Show threadHallå KittehJun 16, 2017
https://spideroak.com/personal/semaphor
Show threadHallå KittehJun 20, 2017
I believe #movim also counts as an XMPP frontend for one-on-one or solo conversations, plus it has an asynchronous social network on top.

http://movim.eu/

That reminds me, BuddyCloud is in the wrong category in my original list, just like movim it's primarily an asynchronous social network, but probably (?) like movim (?) also has its own front-end for good old XMPP one-on-one and MUCs.
Show threadHallå KittehJun 20, 2017
s/solo/group/ :-)

Although solo is supported too. :-D
Show thread(-(-_(-_-)_-)-)Jun 16, 2017
@clacke we are using Rocket.Chat ... in Beta test, ... #love them .
We are missing the videoconference ...which might be solved via Jitsi Meet ( Videobridge ) . Work in progress...

 And MIT license . Naturally.
Show threadHallå KittehJun 16, 2017
@jordila Their website turned my CPU into a furnace the first time I visited it. But I will try not to judge the product against that. :-D
Show thread(-(-_(-_-)_-)-)Jun 16, 2017
@clacke yeah... my Android 4.4 is also starving for 10 secs when launching the app. Remember the software, it is still at Beta stage