On Monday 28 August 2017 22:25:51 Uwe Brauer wrote:
>     > On Monday 28 August 2017 21:34:04 Uwe Brauer wrote:
>     > i'm on linux mint 18.2 mate 64bit
>     >
>     > try with an other keyboard if you have one
>
> Ah, it works with LO OO and with xterm, but not anymore with kde konsole
> and worse it does not work anymore with seamonkey or thunderbird.
>
> Not sure what to do?
>

ok, i think i solved your problem.
keyboard layout > xkb options

pick a "compose key position" that suites you
for example left winkey, then....
win+"+a = �

if that doesn't work, go kill a kitten.