xmodmap

xmodmap -pke

-showing all key prefs

xev

-you can check which key is which number

my default 49 was

keycode 49 = Escape asciitilde Escape asciitilde

and I changed to

xmodmap -e 'keycode 49 = grave asciitilde grave asciitilde'

at ibus "Use system keyboard layout" option in Preference -> Advanced.