Samsung is experimenting with a new feature in South Korea that can hide your data
from nosy repair technicians. Its called “Repair Mode“, when its
enabled the device will hide all your photos, documents, third-party apps,
accounts, and messages.
You will be able to use the device even when the ‘repair mode’ is enabled, it’s
just that all the user data will be hidden. This feature will definitely make
leaving your phone in a repair shop a lot less scary.
According to Samsung, this feature will be in an upcoming update for the
South Korean version of the S21 series. And, you should be able to find it
in Settings > Battery and Device Care > Repair Mode.