remove-supplementary-materials.xsl

<xsl:stylesheet version="3.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

  <xsl:output method="xml"/>

  <xsl:template match="@*|node()">
    <xsl:copy>
      <xsl:apply-templates select="@*, node()"/>
    </xsl:copy>
  </xsl:template>

  <xsl:template match="sec[@sec-type='supplementary-material']"/>

  <xsl:template match="body">
    <xsl:copy>
      <xsl:apply-templates select="@*"/>
      <xsl:apply-templates/>
    </xsl:copy>
  </xsl:template>

</xsl:stylesheet>