rtl8821cu_bluetooth_driver
Linux_BT_USB_v3.10_20170314_8821CU_BTCOEX_20170223-1111
Originally obtain from a chinese manufacturer COMFAST, if you are seeking support for android or Windows, or macOS, just download this big All-in-one archive file: http://www.comfast.cn/download/qdcx/item-563.html