After clicking on "replace world" and choosing a MCPE world in the Realm settings, the world is going to export. After exporting successfully, the world starts uploading itself to the Realm. But after 10 hours, not even 1 KB was uploaded to the Realm, yet.
Related issues
Attachments
Comments
migrated
[media]
migrated
This resembles https://bugs.mojang.com/browse/REALMS-184, same problem I am having. 😞