The IonCube Loaders for PHP 7.2 were released two days ago. Here is how you can quickly enable them for users on Plesk Onyx for Linux:
Download the Latest Version
wget https://downloads.ioncube.com/loader_downloads/ioncube_loaders_lin_x86-64.tar.gz
Extract, Copy & Enable the Loader
tar -xvf ioncube_loaders_lin_x86-64.tar.gz
cp ioncube/ioncube_loader_lin_7.2.so /opt/plesk/php/7.2/lib/php/modules/
echo "zend_extension=ioncube_loader_lin_7.2.so" > /opt/plesk/php/7.2/etc/php.d/00-ioncube-loader.ini
Make Available in Plesk
/usr/local/psa/bin/php_settings -u
You can verify that it was successfully loaded by typing:
/opt/plesk/php/7.2/bin/php -v