HubSpot - Google Tag Manager - GDPR Opt-Out Listener.

hubspot-gtm-gdpr-cookie.js

if ({{Cookie Opt-Out}} !== 'false') { // Cookie Opt-Out would be whatever you name your GTM variable for the first party cookie
    _hsq.push(['addPrivacyConsentListener', function (consent) {
        if (consent.allowed == false) {
            var cookieName = "cookiesOptOut"; // the name of the first party cookie in your GTM account to track cookie opt-in
            var cookieValue = false;
            var cookiePath = "/";
            var expirationTime = 31536000; // consent needs to be tracked for 1 year before asking again under GDPR
            document.cookie = cookieName + "=" + cookieValue + "; expires=" + expirationTime + "; path=" + cookiePath; // sets the cookie for opting out
        }
    }]
)};