If there is no filter to change the content, the other option is to add a function hooked to gettext
– for example:
/**
* Change text strings
*
* @link http://codex.wordpress.org/Plugin_API/Filter_Reference/gettext
*/
function wpse_382257_text_strings( $translated_text, $text, $domain ) {
switch ( $translated_text ) {
case 'Check your email for the confirmation link, then visit the login page.' :
$translated_text = __( 'SOMETHING ELSE', 'text-domain' );
break;
case 'Another' :
$translated_text = __( 'Whatever..', 'text-domain' );
break;
}
return $translated_text;
}
add_filter( 'gettext', 'wpse_382257', 20, 3 );
ref: https://developer.wordpress.org/reference/hooks/gettext/