Thank you for your message. The recommended hardware for webOS guide has been updated with new models that are now supported. You should find that the guide lists the same models as the Firmware matrix, which you can use to see what Firmware version is recommended for use with the Xibo Player:
The 75UM3E is listed in the guide and matrix because it is indeed a supported model. The model you mentioned in your original message, 75UM3B is not a supported model.