I am experiencing the same issue. I have a OnePlus 6T with the latest updates applied. It appears as though a blank note is opened, and if you wait, eventually the note loads. I first noticed it this weekend when a notebook with a high note count took an excessively long time to load the notebook contents. Eventually though, the app is unstable and becomes unresponsive for me and I have to close it and re-open it.
In my case, I can safely my internet connection isn't the issue. My device also has more than sufficient resources, and in reviewing some of the other devices listed, I would infer the same.
I have a support request submitted. I did, however, want to comment as it appears I'm not the only user experiencing the problem.
If there are additional details that I can provide, please let me know. I'd like to do my best to help narrow down the source of the issue.