on the portal of power apps the page for Knowledge article doesn't work with form entity which is a struggle in order to be provided multiple functionalities or more specific to be add a sub-grid. Recently I have a customer who is not able to set a share-point sub-grid on the knowledge article page where his customers can upload additional information. The current work-around is to ad notes in the Knowledge article page but in this way his customer are not able to upload files, which is not the desired result.
My suggestion is:
The knowledge article page to be able to work with entity form where you can add sub-grid with different functionalities.