Use RankMath title for MightyShare.io renders in WordPress https://mightyshare.io/

rankmath-mightyshare-title.php

<?php
// If RankMath is active & a meta title is set use it with MightyShare instead of post title
function mightyshare_use_rankmath_seo_title( $template_options ) {
	if ( in_array( 'seo-by-rank-math/rank-math.php', apply_filters( 'active_plugins', get_option( 'active_plugins' ) ), true ) ) {
		global $post;
		$rankmath_title = RankMath\Post::get_meta( 'title', $post->ID );
		if(!empty($rankmath_title)){
			// Use RankMath title for MightyShare
			$template_options['title'] = $rankmath_title;
		}
	}
 
	return $template_options;
}
add_filter( 'mightyshare_filter_post', 'mightyshare_use_rankmath_seo_title', 10, 3 );