What's the model number of your Roku device displayed under Settings->System->About? If it's 4400, you have no choice but to buy a new device if you want to continue using Hulu and Disney+.
[OOPS -- There is no model with a model name of Ultra 4K, which is why renojimasked for your actual model number. I picked up on Jim's reference to Roku 4400 (model name Roku 4) in Jim's reply. If you don't have a Roku 4 model 4400, please ignore what follows:]
Your Roku 4 was released in 2015 and Roku now considers it a legacy device. As such it is no longer receiving updates, beginning with the release of Roku OS version 12.0 in March of this year. The last version running on Roku 4 is version 11.5.
Many channels, most in fact, will continue to run on your unit for now, but Disney has decided to drop support for the Roku 4 on the various streaming channels it operates, mainly Disney+, Hulu, and ESPN.
It is a safe assumption that, now that Roku has stopped updating it, other channels will start dropping Roku 4 in coming months, as it uses a unique processor no other model has, and support for it complicates the programming of the various channel apps.
