Some services have settings on their websites that affect the maximum bitrate they'll give you, so you might start there. Other than that, the only thing I can think of is connecting a Roku device to your TV and adjusting its display type to 720p since you can't do it on a Roku TV.
If you're just looking for something to be on 24/7, you might want to try an antenna to see what you can pick up. It won't use any data.
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