We use automation to send reminder emails (ITIL 3 strike rule) to customer/ticket reporter. The email message starts with "Hi Firstname". Below code does that for us.
{{issue.reporter.emailAddress.substring(0,1).toUpperCase()}}{{issue.reporter.emailAddress.substring(1, issue.reporter.emailAddress.indexOf("."))}}
Cheers,
Sami
You may use the capitalize() function, adding it to the end of the expression:
https://support.atlassian.com/cloud-automation/docs/jira-smart-values-text-fields/#capitalize--