For chat, consider setting up your own Murmur server [1] and use Mumble to do voice and text chat. It is not has happy-clicky as Discord, but the sound quality is great and you can have thousands of people on a tiny VM. It is very easy to deploy. It looks like people have created ansible playbooks for this too. [2]
[1] - https://wiki.mumble.info/wiki/Main_Page
[2] - https://github.com/systemli/ansible-role-mumble
P.S. use their 1.3 RC version. It is very stable and much better than 1.2.