First-time Samsung has added the feature of s pen in Samsung galaxy s series phone. Before this feature of s pen is in only the Samsung note series. This feature is the main highlight of Samsung note phones.
This option isn’t available for the Galaxy S21 or S21 Plus. The S pen will only support Galaxy s21 Ultra.
Another main thing is pen will not come with S21 ultra if you want to use this then you have to purchase it separately. And after purchasing it. you have to take care of it have to keep safe because the phone does not have a separate house for keeping as note phones have.
Or You can purchase an inbuilt case cover of s21 ultra keeps your pen. For using s pen Simply tap the tip to the S21 Ultra’s screen and everything should be ready to go.