After upgrade to Mojave, a long press of any letter does not bring up the accented character menu. Instead it disables all letters from being inputted in applications (Messages, Safari, Skype, TextEdit, Chrome and others).
Special keys like
return still work.
If I execute
defaults write NSGlobalDomain ApplePressAndHoldEnabled -bool false, press and hold repeats the letter, and input is not disabled.
If I change it back to
true, input gets disabled after a press and hold.