I have a user which Salesforce Platform License and this user is added to a public group.Dashboard folder has been shared to this public group.
But when I am log-in with this user,I am able to see dashboard folder but on clicking on dashboard,it shows Insufficient privileges error message.Also,this user is able to see reports from other folder that has been shared to this group.
User's profile has Create and Customize Dashboards,Edit My Dashboards and View Dashboards in Public Folders access.