Hi @john.marcello
a boolean function return true or false. so a true / false checkbox return true or false too.
this code should resolve your problem:
target="<?php echo get_field( 'open_where', false, false ) == true ? '_blank' : '_self'; ?>"
so your <a>
link’s code should looks like this:
<a target="<?php echo get_field( 'open_where', false, false ) == true ? '_blank' : '_self'; ?>" href="<?php the_sub_field('video_thumbnail_link'); ?>">
hope this help you
A