Can I detach the HomePod mini cable?
No, the HomePod mini cable is not detachable. It is not recommended to pull on the power cable.
While the HomePod mini is often photographed sans wires, there is a USB-C cable attached to the speaker. The HomePod mini includes a 20W USB-C power adapter in the box.
The HomePod mini can be powered from any USB-C port with high enough wattage.