We recently did this. At first we had our old 1.14 and a fresh 1.17 and tried to export/import the database but kept getting "Fatal Error". I tried a bunch of things including changing how I exported and imported the database, which ost_config file to use, file permissions. Wasted a lot of time.
Then we just did the upgrade on the old server from 1.14 to 1.17, which also took a long time but actually worked. However, we had to upgrade Ubuntu, PHP and MySQL at the same time, so I'd give yourself a few days if that's the case for you too. When we had all that upgraded, following the osTicket Upgrade documentation worked for us.
Just make sure you backup [osticketrootdir]/include/ost_config.php and get the latest versions of any plugins and you'll probably need to uninstall/reinstall the plugins too.