Hi Arcamdc, welcome to the forum!
Please note as outlined here hi res audio is limited to 96KHz/24-bit on Chromecast. As far as I know once you’re streaming audio through Chromecast the SA30 front displays the static text casting Chromecast, nothing more.
It should be possible to hear the difference between a standard CD quality recording and a hi res recording. Try to buy two equal tracks of your favourite album, one track in 16 bit 44k1 and the same track in hi res. Play these tracks sequentially on the SA30.
What is wrong with the MusicLife app? Are you missing some functionality or does the app not work for you?