i also have exact same problem, i tried to mount the external hardesk in the utility but didn't work, and now i'm doing a first aid and its taking ages still didn't show any sign its going to work either!
and yes its only usb 3.0 devices that is not working anymore after the latest update BigSur, i tried everything i even formatted the laptop completely and stuck not able to have older version of the system so i had to reinstall bigsur!
everything important is on that external hardisk all my work my art my health my everything its 1T its years and years .. i'm so sad for not being able to open it!
and every time i see a tutorial about downgrade it needs a usb! i couldn't find anything not required usb!
i won't give up i'll either figure a way to downgrade or fix the usb port by my self!
i'll be updating you!
but i'm very glad there is people like me in this situation because when i contacted apple support they told me this is their first time to hear about such a problem cause by BigSur!
now i know i'm not alone in this!
AlaaJad
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i also have exact same problem, i tried to mount the external hardesk in the utility but didn't work, and now i'm doing a first aid and its taking ages still didn't show any sign its going to work either!
and yes its only usb 3.0 devices that is not working anymore after the latest update BigSur, i tried everything i even formatted the laptop completely and stuck not able to have older version of the system so i had to reinstall bigsur!
everything important is on that external hardisk all my work my art my health my everything its 1T its years and years .. i'm so sad for not being able to open it!
and every time i see a tutorial about downgrade it needs a usb! i couldn't find anything not required usb!
i won't give up i'll either figure a way to downgrade or fix the usb port by my self!
i'll be updating you!
but i'm very glad there is people like me in this situation because when i contacted apple support they told me this is their first time to hear about such a problem cause by BigSur!
now i know i'm not alone in this!