Not sure how to go about syncing a OneNote-page to reMarkable because I’m not sure how to get stuff into the pad without the reMarkable cloud/desktop-app. I’ve searched a little, and it doesn’t seem there are any posibilities here yet.
When it comes to syncing reMarkable to OneNote you may be able to with the OneNote action called “Create Image Note”. You’ll then use a trigger for Office 365 integrations called “New email”, and you’ll filter on the sender (reMarkable). The action says it needs a publicly available image, that may be a problem.