USB pendrive recognition by HA

Hello,

Trying to setup a USB pendrive into a Hassio 0.99.02 on a Raspberry4: I follow the instructions provided at https://www.home-assistant.io/docs/ecosystem/backup/backup_usb/ but I got errors:

output3

Overall, I see the devices are not created in /dev, but in some obscure directories /sys/devices/platform… and are not accesible.

Any idea whats’ going wrong?
Thanks

That guide won’t work with Hass.io