I can reproduce these messages now. I followed "Steps to reproduce the issues" from this link; https://github.com/qgis/QGIS/issues/59220 The key part is to unpack a BINARY package. I was trying to run validate-tree on source packages. Maybe this 'bug' can be closed, but I would suggest improving the tag notes, with clear instructions on how to run appstream validate-tree Regards, Peter