I know that the browser in QGIS has quite a bit of capability for managing GeoPackages and other geodata, but I was wondering if there was a lightweight, standalone tool similar to ArcCatalog?
The QGIS Browser is available as a standalone application and as a panel in QGIS Desktop
It’s also possible to run the QGIS Browser as a standalone application. Like the Browser panel, the standalone Browser helps you navigate through your filesystem and manage your geodata. It also helps you preview or create them and open them in a QGIS project by drag-and-drop
The browser is no longer available as a standalone application, starting with the 3.X releases series. See changelog entry here