I recently upgraded to 20.04 LTS from 18.04 LTS and now both my left and right alt keys are not working when I try to use them for any keyboard shortcuts. I had no issues before upgrading. My keyboard mapping hasn't changed since the update (Macintosh UK).

Any help would be greatly appreciated.

Edit updated with xmodmap output

xmodmap:  up to 4 keys per modifier, (keycodes in parentheses):

shift       Shift_L (0x32),  Shift_R (0x3e)
lock        Caps_Lock (0x42)
control     Control_L (0x25),  Control_R (0x69)
mod1        Alt_L (0xcc),  Meta_L (0xcd)
mod2        Num_Lock (0x4d)
mod4        Super_L (0x85),  Super_R (0x86),  Super_L (0xce),  Hyper_L (0xcf)
mod5        ISO_Level3_Shift (0x5c),  Mode_switch (0xcb)
  • What does xmodmap tell about Alt? Then you could try xev to find out what the key actually do. – jarno Jul 13 '20 at 16:00
  • @jarno thanks - have updated original post with xmodmap output. Looks like the key is triggering ISO_Level3_Shift from xev output. – barnsley92 Jul 13 '20 at 17:50
  • Oh, the table shows it knows only left alt key. Have you tried if setting different keyboard model helps? – jarno Jul 14 '20 at 8:12
  • I've tried setting several different varations of the english language layout in the settings if that's what you're referring to? However this didn't seem to have any effect. – barnsley92 Aug 4 '20 at 8:30
  • 1
    resolved by changing the keyboard model via dpkg-reconfigure - thanks @jarno – barnsley92 Aug 7 '20 at 8:32

I have fixed this by changing the keyboard model via dpkg-reconfigure which then gave options to map the alt key which I could not figure out how to do using the keyboard settings in the GUI.

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