The .so library file is located on UbuntuXPS Hello directory called ioncube_loader_lin_7.2.so
you need to put it in /usr/lib/php/20170718/
Then create a new file called 00-ioncube.ini
in the /etc/php/7.2/fpm/conf.d
and /etc/php/7.2/cli/conf.d
directory which has the file content included above.
Restart php-fpm sudo systemctl restart php7.2-fpm.service