Ubuntu – Apple wireless keyboard does not work

If you mean you have made a change in xmodmap and subsequently the change is only working for the right alt, this could be because you need to clear the current settings for the left alt modifier key before you make the change.

Something like this:

clear Mod1
add Mod1    = Alt_L Alt_R

documentation here: https://wiki.archlinux.org/index.php/Xmodmap

If you mean only one alt key is working initially, before anything is changed with xmodmap, maybe the only one alt key is set up as 'alt'. On english apple keyboards one alt is set up as a third and fourth level key, which allows you to choose alternate letter forms on the keyboard, eg 'ß' with the 's' key.

This was a pain in the button to get working. I really wanted to make a precise answer but I think the tech is a little flaky and the tools are a little trying. I did it once successfully, went to do it again from my notes to make sure my answer was sound and it took me another hour of trying to get it to take. These are the steps I followed on Ubuntu 16.04 (derived from @phireph0x and @danielfbm's answers).

1. Install bluetoothctl:

    sudo apt install bluetoothctl
   

2. Run bluetoothctl. You should see an initial list of connected devices like so:

   [NEW] Controller 23:34:17:64:AF:0E ChromeLinux_A00F [default]
   [NEW] Device 00:19:32:D3:38:01 Pico the Keyboard
   

   It's ok if you don't see the Apple keyboard initially. You should see it by the end of step 5 in the next section.

The remaining steps are from the bluetoothctl command prompt:

1. Set the agent:

   agent KeyboardDisplay
   default-agent
   

2. Turn off the Bluetooth keyboard by removing the batteries. Hold the power button in and wait 10 seconds.
3. Scan for devices: scan on.
4. Turn on the Bluetooth keyboard by reinserting the batteries holding the power button in for 10 seconds. If you don't see the keyboard power light blinking continuously, it's not trying to pair. Try again.
5. Wait for your Bluetooth keyboard to appear in bluetoothctl. This will happen asynchronously while you wait at the prompt. My keyboard popped up after 20-30 seconds.
6. Remove any previous attempts: remove 00:19:32:D3:38:01. Replace 00:19:32:D3:38:01 with your keyboard that popped up in step 5.
7. Wait for your Bluetooth keyboard to pop up again. This will probably take 20-30 seconds.
8. Make a connection and pair the Bluetooth keyboard: connect 00:19:32:D3:38:01. Replace 00:19:32:D3:38:01 with your keyboard that popped up in step 5 and 7.
9. If you're on track, you should see your prompt change from: [bluetooth]# to [Pico the keyboard]: .
10. Now, on your Bluetooth keyboard, type 1234 and press enter. That's five keystrokes on the Bluetooth keyboard: 1, 2, 3, 4, and the carriage return.
11. If that worked, you should see the prompt change to:

    [agent] Enter the pin code:
    

12. On your other keyboard, not your Bluetooth keyboard, type 1234 and press enter.

If all works well, you should see Connection successful. If the connection failed, turn off the keyboard and try again from step 2.

Troubleshooting:

• The keyboard seems to mate for life and will try to pair with any Macs it has paired with in the past. Make sure they're off.
• Restart your PC if all else fails. I was surprised to find that I didn't seem to have much trouble with the Ubuntu Bluetooth stack. I did restart a couple times but I don't think it's what got things working in the end.