@günter – no news on this after such a long time? Digging up this thread from the past :-)

The current Update Documentation simply refers to the Envato plugin. So yes, there IS the envato plugin, but they explicitly say:
“Authors are encouraged to implement this plugin in their items so that customers have a reliable and consistent experience across products.”

The Envato plugin is not in the WP repository and so can also not be managed via wpcli. So for our aim to manage plugins completely via WPCLI, this doesn’t help. From all 50+ plugins or themes I manage for different sites, there are just two (yours and one more I won’t name) that can not be managed this way. WPCLI does not appear on the roadmap/upcoming-fixes page, but command line updates are crucial for automated workflows,

Regards
Ulrich