Removing default footer links

Theme Editor

You can remove the whole footer links block using theme editor: Footer Layout

Layout XML

Create a custom Argento theme
Create/add Magento_Theme/layout/default.xml in your custom theme

Add following content to it:

<?xml version="1.0"?>
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
    <body>
        <!-- Privacy policy -->
        <referenceBlock name="privacy-policy-link" remove="true"/>

        <!-- Search terms -->
        <referenceBlock name="search-term-popular-link" remove="true"/>

        <!-- Advanced search -->
        <referenceBlock name="catalog-search-advanced-link" remove="true"/>

        <!-- Guest form link -->
        <referenceBlock name="sales-guest-form-link" remove="true"/>

        <!-- Swissup Sitemap foter link -->
        <referenceBlock name="sitemap-link-footer" remove="true"/>
    </body>
</page>

Magento 2: Removing default footer links

Theme Editor

Layout XML