If an external drive isn't appearing on your desktop or in Finder, first verify the cable connection and port, then open Disk Utility to see if the drive is listed there but requires mounting or first aid repairs.
Have you considered:
media utility performance benchmarks on Big Sur with Intel Iris
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Read our expert take:
While both methods achieve similar results, using the built-in Screen Time settings for limiting app usage tends to be more system-integrated and reliable than relying on third-party timers that may not block access as effectively.