data contains the application’s data assets,
 such as fonts or images

In addition to these files, your application also
relies on various operating system libraries that
it’s been compiled against.
You can see the full list by running ldd
against your application. For example,
assuming you have a Flutter desktop application
called linux_desktop_test, you could inspect
the system libraries it depends upon as follows:

flutter build linux

-release

ldd build/linux/release/bundle/linux_desktop_test

To wrap up this application for distribution
you need to include everything in the bundle directory,
and make sure the Linux system you are installing
it on has all of the system libraries required.
This may be as simple as:

sudo apt-get

install libgtk-3-0 libblkid1 liblzma5