bluetooth is not working in ubundu 16.04 LTS. it shows that "No bluetooth adapters found" .

Same problem here. Used to work and no it does not.

Status changed to 'Confirmed' because the bug affects multiple users.

I apologize for a double post but this looks like the better thread to report this, despite it's age. Everything was working perfectly until the massive update that came out last night, 06/06/2018. Now cannot find internal Atheros BT adapter in Blueman-applet. It appears to allow me to enable BT. Lights on but no one home. Appears to me the Linux BT firmware is borked, again.

user@UX32VD:~$ rfkill list
0: phy0: Wireless LAN
 Soft blocked: no
 Hard blocked: no
1: hci0: Bluetooth
 Soft blocked: no
 Hard blocked: no
2: asus-wlan: Wireless LAN
 Soft blocked: no
 Hard blocked: no
3: asus-bluetooth: Bluetooth
 Soft blocked: no
 Hard blocked: no

user@UX32VD:~$ dmesg | grep Blue
[ 2.999406] Bluetooth: Core ver 2.21
[ 2.999422] Bluetooth: HCI device and connection manager initialized
[ 2.999425] Bluetooth: HCI socket layer initialized
[ 2.999428] Bluetooth: L2CAP socket layer initialized
[ 2.999434] Bluetooth: SCO socket layer initialized
[ 3.020951] Bluetooth: hci0: don't support firmware rome 0x11020000
[ 3.028458] Bluetooth: hci0: don't support firmware rome 0x11020000
[ 4.600699] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[ 4.600704] Bluetooth: BNEP filters: protocol multicast
[ 4.600709] Bluetooth: BNEP socket layer initialized

user@UX32VD:~$ lspci -knn | grep Net -A2; lsusb
03:00.0 Network controller [0280]: Qualcomm Atheros AR9462 Wireless Network Adapter [168c:0034] (rev 01)
 Subsystem: Bigfoot Networks, Inc. Killer Wireless-N 1202 Half-size Mini PCIe Card [1a56:2003]
 Kernel driver in use: ath9k
 Kernel modules: ath9k
Bus 002 Device 004: ID 0cf3:3004 Atheros Communications, Inc. AR3012 Bluetooth 4.0
Bus 002 Device 003: ID 04f2:b330 Chicony Electronics Co., Ltd Asus 720p CMOS webcam
Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 003: ID 0bda:0139 Realtek Semiconductor Corp. RTS5139 Card Reader Controller
Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

user@UX32VD:~$ lsusb; dmesg | egrep -i 'blue|firm'
Bus 002 Device 004: ID 0cf3:3004 Atheros Communications, Inc. AR3012 Bluetooth 4.0
Bus 002 Device 003: ID 04f2:b330 Chicony Electronics Co., Ltd Asus 720p CMOS webcam
Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 003: ID 0bda:0139 Realtek Semiconductor Corp. RTS5139 Card Reader Controller
Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
[ 0.316322] [Firmware Bug]: ACPI: BIOS _OSI(Linux) query ignored
[ 2.361902] psmouse serio4: elantech: assuming hardware version 4 (with firmware version 0x361f02)
[ 2.999406] Bluetooth: Core ver 2.21
[ 2.999422] Bluetooth: HCI device ...

Zero if you are using kernel 4.15 add yourself to the affected by on https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1764645
As that is the bug that affects you, not this old one

This is now working again as of Linux-Firmware 1.157.20 and kernel 4.4.0.130.136 received today.

THANK YOU, THANK YOU, THANK YOU!!!