Note: S.M.A.R.T. status info can't be read from USB attached drives. You have no idea if they're throwing errors indicating imminent doom.

On FreeBSD getting S.M.A.R.T. status over USB drive works without any problem:

    # smartctl -a /dev/da0
    smartctl 7.4 2023-08-01 r5530 [FreeBSD 13.2-RELEASE-p1 amd64] (local build)
    Copyright (C) 2002-23, Bruce Allen, Christian Franke, www.smartmontools.org
    
    === START OF INFORMATION SECTION ===
    Model Family:     Western Digital Elements / My Passport (USB, AF)
    Device Model:     WDC WD50NDZW-11A8JS1
    Serial Number:    WD-WXP2EA07UYLA
    LU WWN Device Id: 5 0014ee 2be7aef41
    Firmware Version: 01.01A01
    User Capacity:    5,000,947,523,584 bytes [5.00 TB]
    Sector Sizes:     512 bytes logical, 4096 bytes physical
    Rotation Rate:    5400 rpm
    Form Factor:      2.5 inches
    TRIM Command:     Available, deterministic
    Device is:        In smartctl database 7.3/5528
    ATA Version is:   ACS-3 T13/2161-D revision 5
    SATA Version is:  SATA 3.1, 6.0 Gb/s (current: 6.0 Gb/s)
    Local Time is:    Sat May 11 10:26:04 2024 CEST
    SMART support is: Available - device has SMART capability.
    SMART support is: Enabled
    
    === START OF READ SMART DATA SECTION ===
    SMART overall-health self-assessment test result: PASSED
    
    General SMART Values:
    Offline data collection status:  (0x00) Offline data collection activity
                                            was never started.
                                            Auto Offline Data Collection: Disabled.
    Self-test execution status:      (   0) The previous self-test routine completed
                                            without error or no self-test has ever 
                                            been run.
    Total time to complete Offline 
    data collection:                ( 4680) seconds.
    Offline data collection
    capabilities:                    (0x1b) SMART execute Offline immediate.
                                            Auto Offline data collection on/off support.
                                            Suspend Offline collection upon new
                                            command.
                                            Offline surface scan supported.
                                            Self-test supported.
                                            No Conveyance Self-test supported.
                                            No Selective Self-test supported.
    SMART capabilities:            (0x0003) Saves SMART data before entering
                                            power-saving mode.
                                            Supports SMART auto save timer.
    Error logging capability:        (0x01) Error logging supported.
                                            General Purpose Logging supported.
    Short self-test routine 
    recommended polling time:        (   2) minutes.
    Extended self-test routine
    recommended polling time:        ( 560) minutes.
    SCT capabilities:              (0x30b5) SCT Status supported.
                                            SCT Feature Control supported.
                                            SCT Data Table supported.
    
    SMART Attributes Data Structure revision number: 16
    Vendor Specific SMART Attributes with Thresholds:
    ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
      1 Raw_Read_Error_Rate     0x002f   200   200   051    Pre-fail  Always       -       0
      3 Spin_Up_Time            0x0027   253   253   021    Pre-fail  Always       -       3508
      4 Start_Stop_Count        0x0032   096   096   000    Old_age   Always       -       4626
      5 Reallocated_Sector_Ct   0x0033   200   200   140    Pre-fail  Always       -       0
      7 Seek_Error_Rate         0x002e   200   200   000    Old_age   Always       -       0
      9 Power_On_Hours          0x0032   083   083   000    Old_age   Always       -       12789
     10 Spin_Retry_Count        0x0032   100   100   000    Old_age   Always       -       0
     11 Calibration_Retry_Count 0x0032   100   100   000    Old_age   Always       -       0
     12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       139
    192 Power-Off_Retract_Count 0x0032   200   200   000    Old_age   Always       -       58
    193 Load_Cycle_Count        0x0032   192   192   000    Old_age   Always       -       24665
    194 Temperature_Celsius     0x0022   086   083   000    Old_age   Always       -       66
    196 Reallocated_Event_Count 0x0032   200   200   000    Old_age   Always       -       0
    197 Current_Pending_Sector  0x0032   200   200   000    Old_age   Always       -       0
    198 Offline_Uncorrectable   0x0030   100   253   000    Old_age   Offline      -       0
    199 UDMA_CRC_Error_Count    0x0032   200   200   000    Old_age   Always       -       0
    200 Multi_Zone_Error_Rate   0x0008   100   253   000    Old_age   Offline      -       0
    
    SMART Error Log Version: 1
    No Errors Logged
    
    SMART Self-test log structure revision number 1
    No self-tests have been logged.  [To run self-tests, use: smartctl -t]
    
    Selective Self-tests/Logging not supported
    
    The above only provides legacy SMART information - try 'smartctl -x' for more

That's interesting, it appears I may have been slightly mistaken.

As per https://www.smartmontools.org/wiki/USB:

> To access SMART functionality, smartmontools must be able to send native ATA or NVMe commands directly to the drive. For USB devices, at least the following conditions must be met:

> The USB bridge provides an ATA or NVMe pass-through command.

> This command is supported by smartmontools.

> The operating system provides a SCSI pass-through I/O-control which works through its USB-layer.

> SCSI support is implemented in the operating system interface of smartmontools.

So in some cases, it may work depending on the USB chipset capabilities. I haven't gotten it to work on my old supermicro.. yet :) Cheers.