I’ve pushed a partial fix to make it work with the latest Discourse version. However, this fix only addresses the autocomplete feature. 
Currently, I am unable to resolve the issue with the emoji picker. Recently, the team has unified the emoji picker with the chat in https://github.com/discourse/discourse/pull/28277. Unfortunately, the plugin outlet in the emoji picker footer, which was previously used to insert a toggle, has been removed in the new version. At this moment, I do not have a solution. Sorry for the inconvenience! 