Bluetooth stopped working

[Schwarzer Kater]

PS:

Sorry - I forgot something…
With my suggestion you will always have to enter the "Advanced options for …" in the GRUB boot menu, though, to select the older kernel.
If you want to avoid this you can disable the submenu structure in the GRUB boot menu. To do this in Kate open the /etc/default/grub file again and add the line
GRUB_DISABLE_SUBMENU=true
save the file again and in Konsole enter sudo update-grub again (or do it all in one go with the changes I posted above, of course).
Now the older kernel should be directly preselected if you have booted with it before.

I also added this above.

[oshunluvr]

Another method to boot to the previous kernel without user input is, again in /etc/default/grub, change this line:

GRUB_DEFAULT=0

to:

GRUB_DEFAULT="1>2"

and run "sudo grub-update".
This will select the second kernel (the older one) in the "Advanced options" menu.

To explain in more detail just on case anyone is interested, here's what a "standard" Kubuntu grub main menu looks like:

Ubuntu
Advanced options for Ubuntu

If you select "Advanced options for Ubuntu" for get a sub menu that looks like this:

Ubuntu, with Linux 6.8.0-31-generic
Ubuntu, with Linux 6.8.0-31-generic (recovery mode)
Ubuntu, with Linux 6.8.0-28-generic
Ubuntu, with Linux 6.5.0-28-generic (recovery mode)

Remembering that computer geeks count from zero, not one, the GRUB_DEFAULT="1>2" option means;

"Pick the second item in the main menu (the "Advanced..." sub menu) and the third item in the sub menu, which is "Ubuntu, with Linux 6.8.0-28-generic"

So if we call 6.8.0-31 the "first kernel" and 6.8.0-28 the "second kernel", "1>2" points GRUB to the second installed kernel.

One important note about this option is when you install a new kernel, the previous second kernel will be removed leaving you booting to the previous first kernel. So you have to keep an eye on your updates.

[oshunluvr]

Another suggestion instead of all the grub maneuvering, you might consider uninstalling the kernel that does not detect your bluetooth device. This will likely leave you with only one kernel, which can be dangerous, so I would also recommend installing another, older kernel that works (one previous to the one you're using now) and NOT running autoremove until you get to a new kernel that "sees" the bluetooth device. Then you can clean up and be back to normal. This is clearly a bug and will probably be fixed soon.

[oshunluvr]

Well thank you so much, In fact I found 3 versions of grub and I booted from the 2nd one. I'll follow you advice and hopefully all will be well.

This means you found three kernels in the GRUB menu? If so, I would just remove the one that does not work and leave GRUB alone. Then wait for the next update to a newer version.

From now on as a newer kernel is installed, test it until you get one that works and then you're good to go.

[Schwarzer Kater]

GRUB_DEFAULT="1>2" is certainly the more "elegant" solution.
But I think modifying GRUB by the four changes as I suggested is the more "fool-proof" one - you won't have to actively keep an eye on your (kernel) updates as you will see at once that there is a new kernel at the top of GRUB's boot menu list when one has been installed by updating the system. And then you can calmly decide when it fits best to test the new kernel without having to do anything until then.