I've briefly read through man pkcon, and PackageKit does not seem to provide a command to clear the cache. I think, you already got the best command to clear the cache. If you don't use Gnome Software/PackageKit, just disable (mask) the service.
I've briefly read through man pkcon, and PackageKit does not seem to provide a command to clear the cache. I think, you already got the best command to clear the cache. If you don't use Gnome Software/PackageKit, just disable (mask) the service.
EDIT: Another method is to tell PackageKit not to cache (store) packages - there is a setting in /etc/PackageKit/PackageKit.conf: uncomment #KeepCache=false (to make it look like: KeepCache=false)
gsettings set org.gnome.software download-updates false