Check this link: http://superuser.com/a/171162/384610 (it's for Windows XP but works for Windows 10 as well)
Make sure the key isn't configured as hot-key in your operating system. KeePass 2 uses ALT_GR + A for 'Global auto-type'. See https://superuser.com/a/553138/384610 for how to disable this hot-key.
Gnome requires additional layouts to be activated with this command:
gsettings set org.gnome.desktop.input-sources show-all-sources trueSee https://www.reddit.com/r/gnome/comments/7jqvl9/eurkey_layout_missing_from_the_settings.
[keyboard]For a system-wide configuration, edit
/etc/X11/xorg.conf.d/00-keyboard.confand change the value of
Option "XkbLayout" "eu"
For Windows, I created a registry file that maps the Insert key to AltGr. Making manual changes to the registry may damage your Windows installation. So if you know exactly what you are doing, and you know how to remove registry entries, you can try out the mapping. Here's to acitvate it, InsertToAltGr.reg, and here's to remove it, RemoveKeyMappings.reg. Again, only run it after having verified the registry files do what you want.
Here's a small guidance I received from someone having problem with the installation and finally managed it:
1. Windows Settings > Time and Language > Region & Language
2. In "Language | Preferred Language", click on any Language, then magically a button "Option" appears.
3. Keyboards > Add a keyboard > Add EurKey