Your WebOS version 04.30.02. From what I could find online, it appears there is an issue with that update. I would suggest to contact LG directly. https://www.cnet.com/forums/discussions/lg-49uh6100-update/
Just spoke with the Disney+ Support, the App will be available from the official Start, tomorrow for all LG TV 2016+ and WebOS 3.0+ in the LG Content Store.
The same for Android or FireTV. So it is not possible to preinstall it.
For the LG 55LB650V it will not be available, so I have to find there an different solution, maybe an FireTV Stick. 🤔