If you’re looking to give your app users a link and an experience that is limited to just your application - or potentially a few related applications - I’d recommend configuring a Carbon workspace.
This will create a permalink that will open this workspace and, as part of the configuration, you can control if and how users can “discover” the rest of Foundry.
The embedded=true flag to hide the sidebar is, as the query parameter implies, intended for use when including a portion of Foundry embedded within some other UI, either within or external to Foundry.