odoo16/addons/payment_adyen/views/payment_templates.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>

    <template id="checkout" inherit_id="payment.checkout">
        <xpath expr="." position="inside">
            <t t-call="payment_adyen.sdk_assets"/>
        </xpath>
    </template>

    <template id="manage" inherit_id="payment.manage">
        <xpath expr="." position="inside">
            <t t-call="payment_adyen.sdk_assets"/>
        </xpath>
    </template>

    <template id="sdk_assets">
        <script src="https://checkoutshopper-live.adyen.com/checkoutshopper/sdk/4.7.3/adyen.js"
                integrity="sha384-YiT4BfPwbplFwUnpDjm2rmWCvpzdi6+l+1E+J9JKTB3CYyKbbwJ8ghkUheQf79X9"
                crossorigin="anonymous">
        </script>
        <link rel="stylesheet"
              href="https://checkoutshopper-live.adyen.com/checkoutshopper/sdk/4.7.3/adyen.css"
              integrity="sha384-X1zQUhO5NGWdMQmDcuv2kyQK65QR7/VJtNthEImZm7jOvOEicQrnVijI0n9DcHkF"
              crossorigin="anonymous">
        </link>
    </template>

</odoo>