ILIAS
ILIAS is an Open Source web-based Learning Management System (LMS) that provides an integrated e-learning platform that can be adapted to suit various educational and professional settings, making it a flexible and powerful tool for online learning and knowledge sharing.
ILIAS has built-in WOPI support that works with Collabora Online.
Configuration
As the administrator of your ILIAS system, go to the Administration section, Third Party Software.

There, in the Settings tab, select WOPI, click Activate WOPI and enter the WOPI discovery URL for Collabora Online.

Usage
Then after that in the Repository content, you can open any office document in an external editor:

More info
For more information see Ilias installation and maintenance