Hello,
I am not sure how searchguard works.
These are upgrade docs: https://www.elastic.co/guide/en/elastic-stack/current/upgrading-elastic-stack.html
We also need to generate passwords: https://www.elastic.co/guide/en/elasticsearch/reference/current/setup-passwords.html
Please note searchguard is a commercial independent plugin and we don't support it.
Thanks,
Bhavya