Concept of a resilient HID keyboard. Restarts when USB is lost. Waits for UAB to be back.

resilient-HID.py

"""
Resilient HID:
Test at the start to wait for the USB connection to be available
"""
import microcontroller
import supervisor
import time

# wait for connection
while not supervisor.runtime.usb_connected:
    # blink a warning
    time.sleep(1)

"""
Catch any error caused by the disconnection and reset the board to try to re-enumerate
"""
try:
    # put here your main loop
    #
except OSError:
    # reset if we lost USB
    if not supervisor.runtime.usb_connected:
        # show some warning maybe
        print("Resetting because of an error")
        time.sleep(2)
        microcontroller.reset()
    # raise the error if it's something else
    raise