Ubuntu 20.04 cannot pair Bluetooth Keyboard

Dell Vostro 2520
Broadcom Corp. BCM43142 Bluetooth 4.0
Ubuntu 20.04
Windows 10 Pro
Windows 10 Home
Android 11
iPhone ??

I purchased a mini Bluetooth keyboard for use with my Android phone. Brand unknown but the model number is BK3001; there are hundreds available on eBay, Amazon, etc. This keyboard works with Android 11 on my Xiaomi Redmi Note 9 Pro smartphone, Windows 10 Pro* and Home+, and iPhone. But when on Ubuntu 20.04.x I open the Settings app at Bluetooth and it scans for Bluetooth devices forever without noticing my keyboard, imaginatively named "Bluetooth Keyboard".

After searching AskUbuntu again I tried:

~$ bluetoothctl
Agent registered
[bluetooth]# power on
Changing power on succeeded
[bluetooth]# agent on
Agent is already registered
[bluetooth]# default-agent
Default agent request successful
[bluetooth]# scan on
Discovery started
[bluetooth]#

Again discovery finds nothing. Neither does:

~$ hcitool scan
Scanning ...
~$ bt-device -l
No devices found

Shouldn't Bluetooth Just Work? It has been around for quite a while now but although many other devices can find it, Ubuntu 20.04 can't. Any advice please?

* My wife's Lenovo laptop.
+ Dual-booted into Dell Vostro 2520.

1 Answer

It appears that if the Dell Vostro 2025 is suspended and then awakened later, Bluetooth cannot detect any external Bluetooth devices. So here is how to get the Bluetooth Keyboard BK3001 to pair with Ubuntu 20.04.4 LTS:

1. In the device previously paired with Bluetooth Keyboard, unpair the keyboard and switch it off.
2. If a record of the Bluetooth keyboard has been saved in the previous device, delete the record.
3. Switch off (Power Off) your computer completely (no restart).
4. Switch your computer on and make sure Bluetooth is switched off. You may have to do this in the in the menu that drops down from the RH end of the screen title bar and by opening Settings > Bluetooth and setting the toggle switch to off.*
5. Now turn over the Bluetooth Keyboard, switch it on, and press the small black activation button. The faint blue pulsing on the upper right of the top of the keyboard indicates pairing is being attempted.
6. Back at Ubuntu, switch Settings > Bluetooth on.* You should see a list of detected external devices; be patient as the keyboard may take a little while to display the pairing code.
7. When the pairing code appears, type the string of digits and press the Enter key (easy to overlook). Voilá, Ubuntu and keyboard are paired!

* The title-bar menu and Settings > Bluetooth may not synchronise. I have seen one show that Bluetooth is on and the other that it is off. Awakening from sleep also needs to be fixed so that Bluetooth returns to the state is was in before suspension.