Qlik Sense Enterprise in its current state does not allow for read-only Folder Data Connections. The business case would be for IT to generate libraries of QVD data (i.e. governed data) of the main data sources and then give read access to these QVD files to power users. At its current state, all these power users must be granted read/write access to the data connection which means that any power users can break the QVD library by storing something new there or overwriting existing files.
Resolution:
This is a highly requested feature for Qlik Sense Enterprise and we do have an open improvement regarding it. To track the idea and vote for prioritization, see Folder Connections using File System Privileges.
In the meantime, there is no great workaround available. Note that it's unusual to give QVD access to users unless they are highly data literate. To give users self-service capabilities it's better to give them access to finished apps with complete data models and give them the possibility to create new sheets and objects.
