Front Edition now defaults to the material theme.
If you'd like to revert to the old theme, add the following parameter to ametys-front-edition-head calls
<xsl:param name="theme">/plugins/extjs7/resources/classic/theme-triton</xsl:param>
<xsl:param name="theme">/plugins/extjs7/resources/classic/theme-triton</xsl:param>
<xsl:param name="theme">/plugins/extjs7/resources/classic/theme-triton</xsl:param>
If you had a custom theme, you'll need to rebuild it so that it's based on the new version of ExtJS