Linux has sadly many problems when it comes to Bluetooth, or at least, some specific distributions of it.

We have seen a case before where many Bluetooth devices were actually supported by the kernel, but an issue in USB power management caused these devices to not work for a very, very long time on various Linux distributions.

Today, it seems that there is another Bluetooth issue.

Some Bluetooth 5.0 adapters which use the rtl8761b firmware are not working correctly on Ubuntu 20.04 and 22.04 (Possibly other Linux distributions too), because of a bug in loading the correct driver for these devices.

In other words, the driver is there on the system and has no issue, but the only issue is that it is not loaded correctly when the Bluetooth device is plugged to the machine.

You can figure this out if you write the following command in the terminal (After inserting the Bluetooth device):

sudo dmesg | grep bluetooth

And you may see the following output:

mhsabbagh@ryzenpc:~$ sudo dmesg|grep bluetooth
[sudo] password for mhsabbagh:
[ 3.582143] bluetooth hci0: loading /lib/firmware/rtl_bt/rtl8761bu_config.bin failed with error -40
[ 3.582145] bluetooth hci0: Direct firmware load for rtl_bt/rtl8761bu_config.bin failed with error -40

This happens because the rtl8761bu firmware is being requested, but the system should have loaded the rtl8761b firmware, not the rtl8761bu one. The latter may not even exist on your system.

To fix this issue, luckily we don’t need to install or download anything! We just need to create a simple symbolic link to link rtl8761bu driver firmware to rtl8761b one. In this way, any time our system requests the rtl8761bu files it will be instead served the correct rtl8761b ones.

We can do it by applying the following commands in the terminal:

cd /lib/firmware/rtl_bt
sudo ln -s rtl8761b_config.bin rtl8761bu_config.bin
sudo ln -s rtl8761b_fw.bin rtl8761bu_fw.bin

After it, just remove the Bluetooth 5.0 adapter from the computer and plug it again (no restart required), and this time, it should be working.

This bug was first caught in Ubuntu on April 11, 2022, but still not fixed until this very day. Many thanks to the “Bert RAM Aerts” user for suggesting the possible fix.

If you have applied this fix and the Bluetooth adapter worked/didn’t work with you, then tell us in the comments below.

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oldhat

Using KDE Neon, I get ‘failed with error -2’. Your solution works just fine, thanks.

Pappy

lib/firmware/rtl_bt$ sudo ln -s rtl8761b_fw.bin rtl8761bu_fw.bin
ln: failed to create symbolic link ‘rtl8761bu_fw.bin’: File exists

setuid

Just a quick heads-up, these instructions do not work on 20.04 nor 22.04, as tested here with the adapter (B08LVH5BCP) from Amazon using this Realtek chip. The firmware file needed for this adapter apparently does not exist, not even from Realtek themselves. That’s a shame, but back into the return envelope it goes, only 10 minutes old.

Elobrand

I just renamed my current file name to the new one it was looking for and it worked.

Pappy

whats the terminal code

jkm

Worked for Ugreen Bluetooth 5.0 USB Adapter, Ubuntu 20.04.5 LTS

Serge

The problem arose early this year after a kernel update on 20.04, tried a few things but they did not work.
I now stumbled accros this solution.
The problem persists, bluetooth does not allow connections to any device though it looks healthy.
dmesg shows:

[17284.463200] Bluetooth: hci0: RTL: loading rtl_bt/rtl8761bu_config.bin
[17284.463212] Bluetooth: hci0: RTL: cfg_sz 6, total sz 17782
[17284.561197] Bluetooth: hci0: RTL: fw version 0x09002b09
[17286.661128] Bluetooth: hci0: command 0x2038 tx timeout

Asus BT500 usb dongle.

PEterE

So I tried this with a fresh install of Ubuntu 22.04.1 to attempt to install my Insignia adapter (https://www.bestbuy.ca/en-ca/product/insignia-usb-bluetooth-5-0-adapter-ns-pa3bt5a2b22-c-black-only-at-best-buy/15997293) and ran into the following:

1. The adapter is recognized, but doesn’t detect any Bluetooth devices.

2. I needed to change
sudo dmesg | grep bluetooth
to
sudo dmesg | grep Bluetooth

3. The symbolic link command returns the following message
ln: failed to create symbolic link ‘rtl8761bu_config.bin’: File exists

I checked and both the bu and b files are in /lib/firmware/rtl_bt

I tried renaming the bu files and set up the symbolic links, but the adapter still did not work.

poisonff

Had the same issue
Fixed it by using the following :
sudo rm rtl8761bu_config.bin
sudo ln -s rtl8761b_config.bin rtl8761bu_config.bin
sudo rm rtl8761bu_fw.bin
sudo ln -s rtl8761b_fw.bin rtl8761bu_fw.bin

Hope this helps

PEterE

Thanks @poisonff, I tried that as well and it didn’t help, except I renamed the bu files to .bin2 so that I wouldn’t lose them.

PEterE

very interesting idea, I tried it with a live disk version of Fedora and the same issue occurred

therefore it’s likely a kernel issue

I’m trying to track down how to report the kernel issue, but it’s pretty complicated to find the right venue to do that

USR

I had to download the specific driver separately from some other website, and then put it in the path for Kubuntu 20.04

Even then it’s not robust, first time connecting to BT devices after first boot works fine, then if switch BT device to anyother device like mobile and then try to connect to Kubuntu again then it won’t connect.

Same issue with both my BT keyboard Logitech k480 and OnePlus Buds z.

I wish Kubuntu is as robust as Windows in BT connections.

In Win 10 same BT adapter is working seamlessly between devices.

Michael

I am having this problem with an Asus USB-BT-500. My terminal will only take the first line of above. (cd /lib/firmware/rtl_bt) It will not take other two lines. Any ideas?

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