I've just installed Debian 9 and bluetooth can be turned on / off, I can also search for devices, however, it doesn't find any devices at all.
During the OS startup, I'm getting these messages: 
root@debian:/home/ilya# dmesg | grep -i blue [ 5.802583] usb 2-4: Product: Bluetooth Radio [ 13.847857] Bluetooth: Core ver 2.22 [ 13.847873] Bluetooth: HCI device and connection manager initialized [ 13.847875] Bluetooth: HCI socket layer initialized [ 13.847877] Bluetooth: L2CAP socket layer initialized [ 13.847882] Bluetooth: SCO socket layer initialized [ 14.330088] Bluetooth: hci0: rtl: examining hci_ver=06 hci_rev=000b lmp_ver=06 lmp_subver=8723 [ 14.330090] Bluetooth: hci0: rtl: loading rtl_bt/rtl8723b_config.bin [ 14.586509] bluetooth hci0: firmware: failed to load rtl_bt/rtl8723b_config.bin (-2) [ 14.586513] bluetooth hci0: Direct firmware load for rtl_bt/rtl8723b_config.bin failed with error -2 [ 14.586519] Bluetooth: hci0: Failed to load rtl_bt/rtl8723b_config.bin [ 14.586521] Bluetooth: hci0: rtl: loading rtl_bt/rtl8723b_fw.bin [ 14.651453] bluetooth hci0: firmware: direct-loading firmware rtl_bt/rtl8723b_fw.bin [ 14.652068] Bluetooth: hci0: rom_version status=0 version=1 [ 14.652074] Bluetooth: cfg_sz 0, total size 22496 [ 23.658112] Bluetooth: BNEP (Ethernet Emulation) ver 1.3 [ 23.658116] Bluetooth: BNEP filters: protocol multicast [ 23.658125] Bluetooth: BNEP socket layer initialized [ 38.947622] Bluetooth: RFCOMM TTY layer initialized [ 38.947627] Bluetooth: RFCOMM socket layer initialized [ 38.947633] Bluetooth: RFCOMM ver 1.11 [ 4363.037311] Bluetooth: hci0: rtl: examining hci_ver=06 hci_rev=000b lmp_ver=06 lmp_subver=8723 [ 4363.037317] Bluetooth: hci0: rtl: loading rtl_bt/rtl8723b_config.bin [ 4363.058517] bluetooth hci0: firmware: failed to load rtl_bt/rtl8723b_config.bin (-2) [ 4363.058524] bluetooth hci0: Direct firmware load for rtl_bt/rtl8723b_config.bin failed with error -2 [ 4363.058527] Bluetooth: hci0: Failed to load rtl_bt/rtl8723b_config.bin [ 4363.058530] Bluetooth: hci0: rtl: loading rtl_bt/rtl8723b_fw.bin [ 4363.059275] Bluetooth: hci0: rom_version status=0 version=1 [ 4363.059282] Bluetooth: cfg_sz 0, total size 22496