found in last page of dl.sipeed.com/HDK/2_Schematic/Lichee_RV_7001_Schematic.pdf
M.2 67p B.key connectors :
* Back side of the board have 5 pins on the little part
* front side (with screen/SoC/µSDcard reader) 6 pins.

Some cheap "B.key 5+6" female connectors are available here (0.74€ for 2 units):
https://fr.aliexpress.com/item/4001262336295.html