It depends on your model of S21 Ultra.
The global, Exynos models, SM-998B, come with a pre-installed screen protector. Use your fingernail to rub over the front camera cut-out. You should feel a slight ridge.
The U.S. A. Snapdragon models, SM-G998U & SM-G998U1, do not appear to come with pre-installed screen protectors.
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My device... Galaxy Z Fold5 5G 12/512GB (G946B D/S) CSC EUX. Android 14. One UI 6.1
