I noticed a while ago that in group-connected Team Sites, there is a "Shared with us" link below the Documents link in the left nav. Clicking this shows files or folders that have been shared with the O365 Group that owns that site. Specifically, the URL it uses is: https://<TenantName>.sharepoint.com/sites/<SiteName>/Shared%20Documents/Forms/AllItems.aspx?view=3
This is pretty handy and I know of a LOT of use cases in our environment. Because most of the Groups around here use Teams, it would be great to surface that "Shared with us" view in a tab in Teams. We've actually gotten a LOT of buy-in for Teams based on the fact that it's NOT SharePoint (well, they don't know that it's storing stuff in SharePoint), so telling folks to go over to SharePoint to see those files/folders isn't ideal.
So, I go to the Team in Teams and add a tab. I select "Website" (which I've used plenty for Document Libraries and Lists in SharePoint) and plug in that URL above. This works OK for files that are shared (ie: Word docs open in Word Online, etc.), but not for Folders that have been shared. The Folders appear, but when I click on one, I'm prompted to select an application to open the item with (see below).
Yeah! AFAIK there is no way around this currently! The folder itself is not exactly a folder in a library! Its more a view and shortcut to a folder existing on the user who shared the folder's OneDrive!
If you go into sharepoint and click it, it will start OneDrive! Teams don't support this currently