Ideally eventually it will be truly universal (at least on a global scale). In the short term, the question of "citizens only?" is a pretty big complication. It

Ideally eventually it will be truly universal (at least on a global scale). In the short term, the question of "citizens only?" is a pretty big complication. It means countries that start UBI sooner will be incentivized either to discourage or restrict immigration, or to limit it to citizens.