More precisely, here is the construct that works
function append_lom_tags_to_dc( $metatags ) {
// $metatags: array containing the dublin Core metatags generated by Add-Meta-Tags
// Adds additional fields, e.g.
$metatags[‘lom:blabla’] = ‘<meta name=”lom:blabla” content=”‘.get_field(‘lom:blabla’, false, false).'”/>’;
return $metatags;
}
add_filter( ‘amt_dublin_core_metadata_head’, ‘append_lom_tags_to_dc’, 10, 1 );