On 18/11/2024 14:15, Ignas Lapėnas wrote:
> somehow I think you did try
> replugging the usb dongle as a troubleshooting step? If not, that would
> be a one thing to try to fix the issue.

I had tried it, but only very briefly, and not together with a reboot. 
I've now tried unplugging the dongle and shutting down the machine 
overnight, and it made no difference.

However, today I have an unexpected popup window with the error message

   g-dbus-error-quark:
   GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name
   org.blueman.Mechanism was not provided by any .service files (2)

which may or may not be useful further diagnostic information.