See https://github.com/TetraTsunami/linklooker/blob/master/privacy.md

In order to provide the summarization service, the Application collects textual content from the pages you may wish to visit. If you supply an API key, this data is additionally transmitted to the endpoint of your choice for processing and is not stored by the Application.

Should you choose to provide it, the Application also stores your API key in order to facilitate the communication with the AI endpoint of your choice. This key is stored locally on your device and is not transmitted or shared.