At the moment emojis get loaded from an external source, without any reference to the setting "$config['allow_cdn']". This is against the ACP setting and a problem for privacy policy, because a 3rd parties connection will be created without user notice or approval.

See:

phpBB\phpbb\textformatter\s9e\factory.php:

$tag->template = '<xsl:choose>

			<xsl:when test="@tseq">

				<img alt="{.}" class="emoji" draggable="false" src="//twemoji.maxcdn.com/2/svg/{@tseq}.svg"/>

			</xsl:when>

			<xsl:otherwise>

				<img alt="{.}" class="emoji" draggable="false" src="https://cdn.jsdelivr.net/gh/s9e/emoji-assets-twemoji@11.2/dist/svgz/{@seq}.svgz"/>

			</xsl:otherwise>

		</xsl:choose>';

There should be a selfhosted version with the emojis in the latest version in the assests/-directory of phpBB. With CDN enabled, it can stay as it is.