Thanks Martin for the detailed response. I was looking into this POST Custom report layout and formatting - #2 by cfi and followed on how to write Custom Report and Layout.
Below are steps I tried converting my XML Report downloaded from UI to HTML which did not work:
1. root@openvas:/home/aviuser/openvas/source/gvmd-22.4.2/src/schema_formats/HTML# ./generate /root/Downloads/report-bbf467bc-b614-459d-b828-e23bf82c3007.xml
2. root@openvas:~/openvas/source/gvmd-22.4.2/src/schema_formats/HTML# ls
generate HTML.xsl
3. root@openvas:~/openvas/source/gvmd-22.4.2/src/schema_formats/HTML# cat generate
#!/bin/sh
# Copyright (C) 2010-2022 Greenbone Networks GmbH
#
# SPDX-License-Identifier: AGPL-3.0-or-later
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see http://www.gnu.org/licenses/.
# Schema generator script: HTML.
#
# This schema generator creates a single HTML file from the XML schema using
# an XSL transformation via the tool xsltproc.
xsltproc ./HTML.xsl $1
4. ./generate /root/Downloads/report-bbf467bc-b614-459d-b828-e23bf82c3007.xml
Above steps did not work in converting XML Report to HTML. Any thoughts on following:
a) how to use this generate script and HTML.xsl file and convert report in HTML Format
b) Any Document to write .xsl file for me to convert XML to JSON Formats.