Same hardware back in iMac (Intel based) – works fine.Try re-partition of the drive as Mac OS Extended – Same.Try re-partition of the drive as APFS – Same.Create a new admin user (Apple Supports insistence) – Same.Start in Safe Mode (Apple Supports insistence) – Same.After the initial moment of showing, the same disk on a Mac Mini M1 now can’t be seen in disk utility with either USB-C/TB port.Attached to Mac Mini M1 it initially showed in Finder/Disk Utility, but after about 2 minutes ejected itself never to be seen again.A Silicon Power 2TB SSD NVMe M.2 in a SHE-C325 enclosure attached to 2017 iMac 27″ works perfectly whether attached by TB/USB-C or USB-A.The cynics among you may assume I have not been thorough in my troubleshooting. Things tried so far, including talking to Apple support And do work with either connector when attached to an Intel based Mac. The same devices that do work when attached by a standard USB-A connector. They work to some degree, they just don’t work properly they don’t allow attachment of many external USB-C enclosures. The Thunderbolt/USB-C ports on M1 Macs don’t work.

If you are thinking of buying a M1 powered Mac and rely on fast, external, storage via a USB-C interface, you may want to reconsider.

M1 macbook air usb c hub