Persistent chat is different then conversation history. Its a feature
that came for on-premises users and is particularly of interest to
customers in the finance sector. Going forward, we generally believe the
Microsoft Teams will be the right tool. We have no public timing to
share on availability on Teams for EDU customers at this time but I know
there is a lot of planning going on for this.
Microsoft don't really care about on-premise users anymore. If you want persistent chat, on multiple clients, you're probably best looking at on-prem alternatives like HipChat, RocketChat or Mindlink (sits on SfB but is crazy expensive)