Comment 6 for bug 1968604

Also see https://fosspost.org/fix-bluetooth-rtl8761b-problem-on-linux-ubuntu-22-04/. From the article:

<SNIP>
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.
</SNIP>