Comment 6 for bug 1840064

You would need to go to "Language Support" and change "Keyboard input method system" to gcin and also change to gcin in "Input Method." I think after that you should be able to switch input method by Ctrl+Space. When you type, little characters should pop out besides your cursor, and that should be sufficient as a check if gcin works.

Also I just found out clicking Ctrl+Space once to switch to gcin works in url bar and search bar. The needs to click twice quickly thing only only applies to webpage part. Thanks!