I had the same issue as @Jeff_Poulton, although it is not working as expected yet.
If I immediately click the ‘MediaLib’ button after the page loads, I get a white screen.
In order to get the MediaLibDialog component to work I have to first select the editor and type ‘something’. It doesn’t matter what I type, I can add a whitespace and then remove it again, as long as in the information component to the right the text with the label ‘created’ changes from ‘now’ to a time string.
After that it works as expected.
The information component also updates when I edit another field on the same collection type, but this does not fix the dialog.
I suspect something about the Quill editor initializes at the first interaction that the media-library component needs. But I don’t now what or how to find that out.