odoo16/addons/sale_purchase/wizards/sale_order_cancel_views.xml

<odoo>
    <record id="sale_order_cancel_view_form" model="ir.ui.view">
        <field name="name">sale.order.cancel.form.inherit</field>
        <field name="model">sale.order.cancel</field>
        <field name="inherit_id" ref="sale.sale_order_cancel_view_form"/>
        <field name="arch" type="xml">
            <field name="display_invoice_alert" position="after">
                <field name="display_purchase_orders_alert" invisible="True" />
            </field>
            <span id="display_invoice_alert" position="after">
                <span id="display_purchase_orders_alert"
                        attrs="{'invisible': [('display_purchase_orders_alert', '=', False)]}">
                    There are active purchase orders linked to this sale order that are not cancelled automatically! <br/>
                </span>
            </span>
        </field>
    </record>
</odoo>