Overview:
Search for device fails on two machines both with fresh installs of 20.04. One of the machines is a 2011 mac mini which previously
had 16.04 and on that version bluetooth worked flawlessly. The other machine is a new HUNSN i5.
The device - a wireless keyboard that pairs successfully with tablets and smartphones, and did pair successfully and work well on the
previous version of 16.04 on the mac mini.

Diagnostics - bear in mind that I am six years retired from web development on linux platforms and as they say - if you don't use it
a lot, you lose it a lot.

Code follows
status
Code:
● bluetooth.service - Bluetooth service
     Loaded: loaded (/lib/systemd/system/bluetooth.service; enabled; vendor preset: enabled)
     Active: active (running) since Thu 2021-03-25 16:20:27 AKDT; 5 days ago
       Docs: man:bluetoothd(8)
   Main PID: 767 (bluetoothd)
     Status: "Running"
      Tasks: 1 (limit: 9338)
     Memory: 2.1M
     CGroup: /system.slice/bluetooth.service
             └─767 /usr/lib/bluetooth/bluetoothd

Mar 30 16:37:08 mini bluetoothd[767]: Endpoint registered: sender=:1.918 pa…/sbc
Mar 30 16:37:08 mini bluetoothd[767]: Endpoint registered: sender=:1.918 pa…/sbc
Mar 30 16:44:19 mini bluetoothd[767]: Endpoint unregistered: sender=:1.918 …/sbc
Mar 30 16:44:19 mini bluetoothd[767]: Endpoint unregistered: sender=:1.918 …/sbc
Mar 30 16:44:19 mini bluetoothd[767]: Endpoint registered: sender=:1.965 pa…/sbc
Mar 30 16:44:19 mini bluetoothd[767]: Endpoint registered: sender=:1.965 pa…/sbc
Mar 30 16:44:30 mini bluetoothd[767]: Endpoint unregistered: sender=:1.965 …/sbc
Mar 30 16:44:30 mini bluetoothd[767]: Endpoint unregistered: sender=:1.965 …/sbc
Mar 30 16:44:51 mini bluetoothd[767]: Endpoint registered: sender=:1.1004 p…/sbc
Mar 30 16:44:51 mini bluetoothd[767]: Endpoint registered: sender=:1.1004 p…/sbc
Hint: Some lines were ellipsized, use -l to show in full.
dmesg
Code:
dmesg | grep -i bluetooth
[    3.595368] Bluetooth: Core ver 2.22
[    3.595400] Bluetooth: HCI device and connection manager initialized
[    3.595405] Bluetooth: HCI socket layer initialized
[    3.595408] Bluetooth: L2CAP socket layer initialized
[    3.595413] Bluetooth: SCO socket layer initialized
[    3.661703] Bluetooth: hci0: read Intel version: 370810011003110e32
[    3.661706] Bluetooth: hci0: Intel device is already patched. patch num: 32
[    5.154398] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[    5.154401] Bluetooth: BNEP filters: protocol multicast
[    5.154406] Bluetooth: BNEP socket layer initialized
[   18.797688] Bluetooth: RFCOMM TTY layer initialized
[   18.797699] Bluetooth: RFCOMM socket layer initialized
[   18.797706] Bluetooth: RFCOMM ver 1.11
[429794.858320] Bluetooth: hci0: Ignoring error of Inquiry Cancel command
[432924.543959] Bluetooth: hci0: HCI reset during shutdown failed
hcitool
Code:
hcitool dev
Devices:
    hci0    4C:34:88:B5:54:22
lsmod
Code:
lsmod | grep -i bluetooth
bluetooth             581632  41 btrtl,btintel,btbcm,bnep,btusb,rfcomm
ecdh_generic           16384  2 bluetooth
rfkill
Code:
rfkill list
0: phy0: Wireless LAN
    Soft blocked: no
    Hard blocked: no
1: hci0: Bluetooth
    Soft blocked: no
    Hard blocked: no
In addition, crashes are associated with both the use of the Control Center feature and the applet.
Attempts to pair have made on both MATE and GNOME.
Hopefully some of this code will edify wiser heads than I,
and I can get my bluetooth back.
Thanks
Tim