macOS Quick Look provides a convenient way to preview common file types without needing to download them first: select one or more files in Finder and press the space bar.
The issue
The Foldr macOS app can run in one of two file system modes, Apple File Provider or macFUSE. Apple File Provider is the default when the app is first run, as Apple is moving away from third-party kernel extension support (such as macFUSE) and will eventually deprecate it completely.
When the app is using Apple File Provider, Quick Look may appear to offer only generic summary file information rather than a full preview.
When the app is using macFUSE as its file system, Quick Look works as expected with no further configuration required. More information about the two file systems, how to switch between them, and the additional steps needed for macFUSE on M-series (Apple silicon) devices is available in the macFUSE setup article.
The solution: thumbnails
Apple File Provider requires thumbnails to be enabled both on the Foldr server (for each storage location) and in the macOS app on the client device for Quick Look to work correctly.
Enable thumbnails on the Foldr server
Navigate to Files & Storage > Files & Storage > Edit Storage > Advanced tab > Thumbnails, enable the toggle and select the required level of quality.
Enable thumbnails in the macOS app
Thumbnails are disabled in the macOS app by default and must be enabled from the app’s settings menu > Foldr Drive tab.