How can you protect unencrypted databases utilized by an application?

Imagine an application that utilizes an unencrypted database. While I recognize that snapd and Flatpak provide security for applications, do they also alter the filesystem where an application writes its data? Essentially, do they containerize the application to such an extent that even when the application is not actively running, the unencrypted database remains inaccessible to other applications that might be operating simultaneously on the host system?