Not sure what you mean by "not supported" on Roku, but the Spectrum app:Hey folks, I just did an update to the matrix on post #1 on the "Help Me Choose a Streaming Device" thread to include "Notable unsupported apps" for each device.
I know from personal experience that the Spectrum app is no longer supported on Roku devices; browsing some Reddit threads it looks like there are also issues on NVidea Shield. Can anybody point me to a reference for where the Spectrum app is/is not supported for install?