my theme has got a code that looks like this:-

<div class="bs-info-author-block py-4 px-3 mb-4 flex-column justify-content-center text-center">
            
            <a class="bs-author-pic mb-3" href="<?php echo esc_url(get_author_posts_url( get_the_author_meta( 'ID' ) ));?>"><?php echo get_avatar( get_the_author_meta( 'ID') , 150); ?></a>
                <div class="flex-grow-1">
                  <h2 class="title"><?php esc_html_e('By','blogus'); ?> <a href ="<?php echo esc_url(get_author_posts_url( get_the_author_meta( 'ID' ) ));?>"><?php the_author(); ?></a></h2>
                  <p><?php the_author_meta( 'description' ); ?></p>
                </div>
            </div>
             <?php } ?>

I would like this code to make the author posted by, thumbnail image to have alt text. Here is production page, (why mobile phone is regarded as a computer)

Thanks