You can find not any free of charge addon for setting up Google Tag Manager in PrestaShop apart from purchasing a paid out addon. Prestashop also doesn’t give usage of Site code so we can easily insert Tag Manager code but there is still an alternate way by specifically modifying https://www.presta-addons-modules.com/en/seo/prestashop-seo-automatic-hreflang-tags-canonical-tags-on-all-pages.html