1. PHP REQUIREMENT LINK : https://github.com/freescout-helpdesk/freescout#requirements
2. Select (GMT-04:00) Eastern Time (US) in manual installation.
3. In config/app.php add domain_name 'trusted_hosts' => env('APP_TRUSTED_HOSTS', '[[domhost]]'), or else it gives error Untrusted Host 
4. set date.timezone = "America/New_York" in php.ini before manual installation and set the same in cache/config.php, .env and in sql  if there is any change in timezone.
5. Upgrade added since 1.8.194, We use the manual method to perform upgrade as mentioned here in their wiki https://github.com/freescout-help-desk/freescout/wiki/Updating-FreeScout#method-5-update-manually