Kanopy adds Chromecast support
Kanopy is a streaming service free to members of various public libraries (and educational institutions). It's been available for a while (e.g. Ottawa Public Library) added it in late Jun or early Jul 2017. On Tuesday (Sep 12) there was an update to their Android app that added Chromecast support.
I don't know what limitations there might be, but they told me in Jul that they support 1080p if your connection can accommodate it. I suspect the image is being distorted, both A Hard Day's Night and Monsieur Hulot's Holiday both filled my TV, but according to IMDB they are 1.75:1 and 1.37:1, respectively (the latter does look a bit like a stretched SD image on TV). Obviously not really a problem for anything shot in 16:9 or thereabouts.