I ran into the following issue after upgrading my desktop & laptop to Pop OS 22.04 (this OS is based on Ubuntu Linux). After the upgrade, when I log in, the system seems to automatically connect via bluetooth to a Mu-so 2, which is in another room, even though the sound is configured to use a monitor’s built-in speakers and no audio is being played… This happens whenever the system boots even if the connection to a Mu-so 2 is explicitly turned off. The result is that other devices cannot connect to the Mu-so 2.
You can fix this by removing the Mu-so 2 from a list of bluetooth devices, but that has to be done explicitly before the system is shut down. With only Pop OS being available at home, I could not test if this issue is specific to Pop OS or if it applies to Ubuntu 22.04 as well.
The issue was discovered because a member of the household likes to use bluetooth to listen to podcasts on an iPad and suggestions to use the Naim app were to no avail. After breakfast, I turned on a desktop and used it most of the day, but not for listening to anything. In the evening, the iPad could not connect and was asked to fix the problem. I tried a laptop and it also could not connect. Finally, I discovered that the desktop had connected without me knowing it had. Debugging took a bit longer than I would have liked, primarily because that member of the household ignored my request to power off some devices due to not seeing why that might matter.
I image this is really a Pop OS or Ubuntu issue, but it is worth noting because debugging it can take a while and it only shows up when multiple devices are on at the same time.
One enhancement to the Naim app that would be useful in this case is for it to provide the MAC address of the bluetooth device the Mu-so 2 is currently connected to: that could help track down such problems. Initially I didn’t suspect that the desktop machine was involved: I must have connected to the Mu-so 2 from it using bluetooth at some point, but probably a long time ago as a test.