FAQ - iconv() Wrong charset, conversion from 'utf-8' to 'utf-16be' is not allowed
iconv() Wrong charset, conversion from ‘utf-8’ to ‘utf-16be’ is not allowed
Synology servers disable various PHP modules, even though they should be enabled by default.
This includes iconv which is required by webtrees.
The control panel / administration interface for the Synology Box contains an option to
enable PHP modules. Find and enable iconv. Restart the web-server.