I installed Ubuntu Mate 24.04 yesterday and all went well except my AltGr key seems dead. (I need it for all sorts of special characters I use for my job)
Oddly it works fine in Featherpad which is the only app on this machine that didn't come on the MATE ISO, but it is dead in Pluma, LibreOffice, Firefox, etc.
Welcome @Spider to the community!
Hi, @Spider 
I've tested just now the use of AltGr key combinations in an (Virtualbox) VM running a fresh install of Ubuntu MATE 24.04 LTS ("Noble Numbat") - the virtualization host machine is a laptop computer running Ubuntu MATE 22.04 LTS ("Jammy Jellyfish") - and the "ALT GR" key combinations are working well for me in "Pluma", "LibreOffice Writer" and "Mozilla Firefox". For instance, pressing the ALT GR key together with the E key shows the € (Euro currency sign), as expected.
Screenshot:
Additional information about my setup: in the "Keyboard" application (available by hovering over the "Ubuntu MATE Menu" -> "Preferences" -> "Keyboard"):
If I click on that "Keyboard" menu option, then the "Keyboard Preferences" window opens. If I then click on the "Layouts" tab of that window, I can see that I'm using a "Portuguese" keyboard layout and the "Keyboard Model" is a Generic 105-key PC":
Although the "Alt Gr" key combinations are working well for me in this Virtual Machine, this reminds me that I haven't yet completed the "Language Support" in this VM. So, if I go to the Ubuntu MATE Menu -> "Preferences" -> "Language Support":
... I then get a dialog box window warning me that "The language support is not installed completely":
So it may be a good idea to click on that "Install" button, which would prompt to enter out password:
... and, by doing that, the process of language support is completed:
@Spider : Maybe it's worth trying to check the "Language Support" in your case, complete it (if you haven't done that already), and then reboot to see if it helps in your case? As I've written, in my case, the "Alt Gr" key combinations were working well, even without completing the "Language Support", but I see no harm in trying to do that.
I hope this helps
Thanks for your reply.
I installed language support and tried three different keyboard layouts, English, Spanish, and German, and the problem persists in all of them.
but the AltGr key mostly works in FeatherPad which is a QT based program (combinations like AltGr+Shift+E open the Edit menu for example).
I tried remapping the key with xmodmap but that didn't solve the problem either.
I am baffled.
I have a similar problem - AltGr seemed to stop working after upgrade Kubuntu 22.04 -> 24.04; closer examination shows it actually produces TWO characters - the correct one is preceded by ESC (ASCII 27), for example AltGr-a should render Polish character Ä… (aogonek), but instead generates ESC Ä… which breaks most (but not all apps). You can verify if your problem is the same by using cat command in konsole, then typing something with AltGr - if you see ^[ before each character, it represents ESC.
Welcome, @Szymon_Sokol to the community!
Hi Szymon,
To narrow down the search for the bug:
I checked my settings (dutch + dutch keyboard which also needs AltGr for certain characters).
In my case AltGr does not generate an extra ESC and does exactly what it is supposed to do.
So I think it's either a bug that is limited to certain languages (keyboard layouts) or your setup has one or more override options enabled (see keyboard preferences -> options).
If no override options are enabled then it's a bug.
It happened before, see this:
and this
You probably want to file a bug too, so use that site to do that.
Thanks for your reply. I know a bit more now - I have done a fresh install of 24.04 to a separate disk, and the system booted from that disk does not show the mentioned problem, so apparently it is caused by some "leftovers" from the upgrade (my system started as 14.04 LTS and has been upgraded to a new LTS version every two years since…); I'll have to investigate further to find the root cause.
