Collabora is available in the “owncloud” app (owncloud 10.0.1), which can be downloaded from the univention app center.
In the owncloud82 app collabora is not available.
You can either get the owncloud app if you want collabora or you can wait until the migration app from owncloud82 to owncloud is released, which could be in the next few weeks. With the app you can migrate all your data from owncloud 9.1.4 to owncloud 10.0.1 / 10.0.3.
If you don’t want to wait and would install the owncloud app - you should make a clean installation with a new univention corporate server or a new appliance which can be downloaded from here:
and here is the documentation for the owncloud Appliance