Conversation w/ Yuvipanda who has already done quite a lot of research in this area says:
- Mattermost is totally opencore - but we will have to buy a closed source product past a certain size. And, they have a super closed dev process. Not recommended.
- Yuvi has terminated both these instances, and he never got Zulip one to work. It used to be a super complicated process in the past to setup Zulip.
- Zulip is working on being less hard to setup. Reach out to Sumana.
With, this I'm resolving this task now, rest of the conversation to take place in the parent task itself!