We are using MS Teams for CoPs and, because the chat in Teams is lacking in many of the same ways that Yammer does, we are piloting a software called Social Squared by Lightning Tools  

It’s built in SPFX and has some really great extensibility and it’s driven off of Sharepoint lists so all of your data is hosted within the Sharepoint site (not limited to just teamsites, it can be used as a web part on any Sharepoint modern site) and not on a 3rd Party. It manifests as a tab in MS Teams so it’s available from the mobile app, provided that you teach your users to find the tab. It has some relatively robust tagging capabilities, as it’s built on SPFX it has the ability to pull directly from the Sharepoint MMS. Lastly, it’s at a very reasonable price point for the entire tenant. 

We’re in our first year trial but pretty happy with it’s use specifically for forums & threaded discussions within our CoPs. If you want to jump on a call and see it, I’d be happy to do that, so you can get the demo but avoid the sales pitch for now. Hope this helps!

Matthew Morrow
Sr. Knowledge Specialist
CRB
mobile: 816-365-2135