... is required. If you don't want to use Oracle JRE 8, you can use OpenJDK instead, but you need to install as a prerequisite the OpenJFX libraries from OpenJDK. You can install this library from the package manager of your system.
In the official website https://gladivs.com you can find more information and a manual.
Feel free to comment if you have any suggestion, bug, or any other question.