While we start a new thread when running a job with the libzip/libarchive plugins, their progress() and entry() signals still end up running code in ArchiveModel's slots, i.e. on the main UI thread.
In particular this is a problem when loading huge tar/zip archives, because the UI gets basically freezed (e.g. you almost can't close the window).
Ideally at least the ArchiveModel should be moved to another thread.