Layered local packages are displayed as system apps on Silverblue
It seems that local layered packages (that contain AppStream metadata) are displayed as system applications on Fedora Silverblue.
This can be reproduced by layering Google Chrome using the official rpm, then trying to uninstall it from the Installed tab of GNOME Software. It is displayed under "System applications" and there is no "Remove" button on its details page, only a "Launch" one.
It is not possible to uninstall such apps using GNOME Software.
Fedora 32 Silverblue, gnome-software-3.36.0-1.fc32.x86_64