The Samsung Galaxy S21 Ultra will steal some of Note’s thunder as it too will support the S Pen. However, this will be more of an add-on than a native feature. The S21 Ultra retail package will not include a stylus and the phone has nowhere to house the stylus in the first place. Instead, the S Pen will be a separate purchase – either by itself or as part of a bundle with select cases. Those cases are a vital part of the equation as they will house the stylus alongside the phone. S View Flip Cover with S Pen for the Samsung Galaxy S21 Ultra You can see that in these renders...
Source: https://www.gsmarena.com/new_leak_shows_galaxy_s21_ultra_case_designed_specifically_for_the_s_pen-news-47008.php