I have an important update after further investigation. I was able to reproduce the failure again and capture it with btmon.
The btmon traces consistently showed that the connection was failing during BR/EDR authentication with: Authentication Failure (0x05) This happened before any A2DP negotiation started, indicating that the audio profile was not the root cause. After investigating further, I compared the stored BR/EDR Link Keys on my Windows and Ubuntu installations (this is a dual-boot system using the same Bluetooth adapter). The Link Keys were different for the same Echo Dot device. Windows: 03CD43933B547B761522B83780E1D3E2 Ubuntu: C0B33FBD5D0147FA477C0051BDDD91E9 I then manually replaced the Link Key stored by BlueZ in: /var/lib/bluetooth/<adapter>/<device>/info with the Windows Link Key, keeping the same Type and PINLength values. After restarting the Bluetooth service (without re-pairing the device), the Echo connected successfully immediately. This strongly suggests that the authentication failures were caused by mismatched BR/EDR Link Keys rather than an A2DP regression or a BlueZ version issue. At this point, I believe the BlueZ versions I tested were likely unrelated to the failures. The connection problem appears to have been caused by the dual-boot systems having different stored Link Keys for the same Bluetooth device. I still do not know what originally caused the Link Keys to diverge, but I wanted to document this finding since it completely changed the outcome of the investigation. Thank you for your time and for helping investigate this issue. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2159829 Title: Regression in BlueZ 5.72-0ubuntu5.5 prevents A2DP connection to Amazon Echo Dot 4 on Ubuntu 24.04.4 LTS To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/bluez/+bug/2159829/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
