Many of the known issues with respect to SharePoint Online are related to differences in browsers.

Dragging and dropping documents and emails

• Dragging and dropping into SharePoint libraries does not work in Firefox.
• Some users have reported intermittently losing the ability to drag and drop. See our KB article for troubleshooting tips.

Copy To/ Move To not showing all possible locations

• Some users have reported that destination sites do not appear when copying or moving files from one location to another.
  
• Use Browse sites to see more options.
• If you only see the spinning wheel and no sites listed, try using Chrome instead of Firefox.
• Ensure that you have followed your destination site. Go to the site and select the star beside Not following (top right corner).

Users don't have Sites option under Attachments > Browse Web Locations in desktop Outlook

• Currently no known fix or root cause for this. Seems to be isolated to Outlook 2016.