NC 20.0.0 + Collabora 6.4.0: Datasets only open in Dashboard "Recommended Files" application

Datasets like Word, Excel and PowerPoint only open in NC 20.0.0 when using dashboard application “Recommended Files”.
LOKit 6.4-6
Ubuntu 18.04.1 LTS
PHP 7.4.10

In application “Dateien” I am not able to open datasets. Message “Collabora is not setup yet”.

I am encountering the same issue with OnlyOffice. Restarting Apache helps, but after a new login the issue reemerges. I did not get any error message.