If the normal routes to exit Safe Mode as shown by @Fiona26 👍 does not appear to work then consider the following guides in these links.
https://www.imobie.com/android-system-recovery/how-to-fix-safe-mode-wont-turn-off.
However be aware that this could result on the loss of some of your data via the Hard Reset Link below.
https://www.hardreset.info/devices/samsung/samsung-galaxy-s21.
How-do-i-perform-factory-reset-on-my-mobile-device.
Other than this a Samsung Service Centre or Samsung Experience Store can help and or send feedback via your Samsung Members App.
If I can be of any further help then please don't hesitate. Take care. 😎
Daily Driver > Samsung Galaxy s²³ Ultra 512Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "
