I would like to start by telling you how i went from Lotus Notes, via SharePoint to Microsoft Teams.
Since 1997 I have been working on building systems for “collaboration”. The first few years I worked as a Lotus Notes-developer. Lotus Notes was at that time, in my personal opinion, the most effective platform for building good collaboration solutions. With Lotus Notes, i built document management solutions, good process support with automated workflows, ordering and booking systems, intranets and HR solutions. You could basically build most of it.
Best of all was that once you had built a good solution you could save it as a template. This template could then be used to quickly build the same, or similar solution elsewhere.
The replication in Lotus Notes means that you can distribute the load over different servers and you as a user can also replicate the databases so that you can work offline on your local computer when you do not have access to the Internet (this was during the time you did not always have access to fast internet everywhere and all the time).
Files were attached to Notes documents and you could use the email to attach links to the Notes documents which in turn contained those files. That’s how you (or at least i) did it “at that time”…
Private channels in Microsoft Teams are now launched and rolled out to your tenant. You can create private channels for a specific group of team members in a team. Only those people that are added to the private channel will be able to see and write messages in it.
Have you informed your users about your guidelines for using this Private channels? If you haven’t done so, now is the time to do it. In the meantime, you can (read: should) disable Private Channels for a time until everyone knows how it works and how to use it.