caption

Hi vvkk

Try using the link_caption attribute in the shortcode:
https://keesiemeijer.wordpress.com/related-posts-by-taxonomy/#link-caption

Rtl should be working out of the box. If it’s not, it’s probably your theme setting the text direction for galleries.

Without being able to see the related posts there is not much I can do.

Try adding this to customizer “Additional CSS” module:
https://wordpress.org/support/article/appearance-customize-screen/#additional-css

.related-gallery .gallery-caption {
	display: block;
	direction: rtl;
}