I sent this on our social media accounts last week: Invalid consumer key/secret in configuration

It's work in progress. There won't be any beta to try. It'll be stable right from the start as the conversion mainly involves API changes to tried-and-tested functionalities in K2. It's really a meaningless boring job to adapt the codebase to Joomla 4, which could have been avoided if the Joomla team cared a bit about backwards compatibility as we do... C'est la vie :)