There is no other (user, usage and other) data collected, processed or explicitly sent to other devices by this extension.
The extension uses real-time info to decide directly on your machine if it should show a notification, or when a channel is opened, if it should instead switch to an existing tab and such features. However this will never lead to any information leaving your browser.
For questions or data issues, contact firstname.lastname@example.org
When using the YouTube features of the extension, the same applies: requests are sent to the YouTube API Services to get information on channels and their live streams or subscriptions. Never are those requests made in a manner that indicates your YouTube or Google account over the API. The data returned by those requests (username, profile picture, subscribers, video title, video category, video thumbnail, channel IDs, viewer count) will be stored by the extension on your machine and may be removed as soon as associated channels and or users are no longer tracked using the extension.