leaky-paywall-exclude-custom-taxonomy.php

<?php

add_filter('leaky_paywall_filter_is_restricted', 'zeen101_bypass_in_custom_tax', 10, 3);

function zeen101_bypass_in_custom_tax($is_restricted, $restriction_settings, $post_id)
{

    $exclude_term_id = 54; // term id that should never be restricted
    $terms = get_the_terms( $post_id, 'topic' ); // adjust the name of the custom taxonomy here

    foreach( $terms as $term ) {

        if ( $term->term_id == $exclude_term_id ) {
            $is_restricted = false;
        }
    }

    return $is_restricted;
}