Once the stream goes to your PC or phone and can be viewed on those, I thought they would simply be able to cast back to the TV something simpler for the TV to interpret. But it doesn't work.The inability to cast from phone to TV is not related to bandwidth, it relates to your TV's inability to process/playback the 4:2:2 HD stream...
So I'm simply sitting my spare laptop PC beside the TV and connecting them via HDMI cable. That's my 4:2:2 decoding solution and it works fine. Before enabling the PC for a given 4:2:2 channel, I check quickly with my phone to see if the channel is worth viewing.