It is not a bug, but a request for functionality.
Flatpak has a flag to uninstallation to delete application data:
flatpak uninstall App --delete-data
The advantage for the user is the saving of space on non usable data.
On Gnome Software they have a Mackup: https://gitlab.gnome.org/GNOME/gnome-software/-/issues/257
Git commit d85fedadfad5e598e26fe5df13208d93249de0e5 by Aleix Pol.
Committed on 06/05/2022 at 22:25.
Pushed by apol into branch 'master'.
flatpak: Show a warning when uninstalled apps still have data present
Uninstalling from flatpak will only uninstall the app but will leave the
user data in the file system. This adds the option to remove it.
M +20 -1 libdiscover/backends/FlatpakBackend/FlatpakResource.cpp
M +7 -1 libdiscover/backends/FlatpakBackend/FlatpakResource.h
A +29 -0 libdiscover/backends/FlatpakBackend/qml/FlatpakRemoveData.qml [License: GPL(3+eV) GPL(v3.0) GPL(v2.0)]
M +1 -0 libdiscover/backends/FlatpakBackend/resources.qrc
Thanks for the work you do
*** Bug 434181 has been marked as a duplicate of this bug. ***