Try adding this PHP snippet to remove the 3 dots:
add_filter('generate_excerpt_more_output', 'custom_read_more');
function custom_read_more($output) {
$output = sprintf(
' <p class="read-more-container"><a title="%1$s" class="read-more button" href="%2$s" aria-label="%4$s">%3$s</a></p>',
the_title_attribute( 'echo=0' ),
esc_url( get_permalink( get_the_ID() ) ),
__( 'Read more', 'generatepress' ),
sprintf(
/* translators: Aria-label describing the read more button */
_x( 'Read more of the post %s', 'more on post title', 'generatepress' ),
the_title_attribute( 'echo=0' )
)
);
return $output;
}
Adding PHP: https://docs.generatepress.com/article/adding-php/