Gomoku XXL needs no account and no connection for local play, games against the AI, the daily puzzle and the review. Your settings and your puzzle streak are stored on your phone.
The first time you open MULTIPLAYER or RANKING, the game creates an anonymous account, with no email and no password. It holds your nickname, your online statistics and your ranking points, so that other players can see them. SIGN OUT, in the profile, gives up that account.
Ads are served by Google AdMob. In Europe, a consent form asks your choice before any ad. If you refuse, the game requests no ads, and usage statistics stay off. Privacy & ad consent, in the settings, lets you change your choice.
The details are in the privacy policy.