AnswerThe ionCube loader can be installed for PHP 8.1 since Plesk Obsidian 18.0.48.
To install it follow the steps below:
- Log in to Plesk.
- Go to Tools & Settings > General Settings > PHP Settings > PHP 8.1 > Manage PECL Packages and install ioncube_loader:
https://pix.cobrasoft.org/images/2022/12/29/mceclip0.png