The existing SAT SMART Driver extension used to provide access to health data on external drives is limited in macOS Big Sur. We will be working on a replacement, but in the meantime, you will need to use the following procedure to access health data on external drives connected via USB (and FireWire, on the few machines that still have it that also support Big Sur). This procedure applies to Intel Macs only. The SAT SMART Driver does not support Apple Silicon Macs.
Once the SAT SMART Driver has been installed using the existing installation method, perform the following steps.
1. Launch Terminal under macOS Big Sur and issue this command:
sudo /usr/bin/kmutil load -p /Library/Extensions/SATSMARTDriver.kext
2. Type in the administrator password to load the SAT SMART Driver.
3. Eject all USB or FireWire drives from the Mac.
4. Physically disconnect all USB or FireWire drives.
5. Wait about five seconds and then re-connect all USB or FireWire hard drives.
6. From the Lifespan Application, uncheck and re-check Enable Monitoring.
7. Any USB or FireWire drives that support SMART should be listed as supported in the Lifespan menu item.
SMART Health Data will be available until the next reboot, after which this procedure will need to be repeated.