@antimage I am not seeing the linked post.
The information I was missing was what /local was.
I have suggested this gets added to the Google Cast documentation;
To cast media stored in your Home Assistant instance, it needs to be added to the /config/www folder which translates to the /local folder. e.g. a cast location of /local/media/audio/test.mp3 is actually stored in /config/www/local/media/audio/test.mp3 . There is no need to define the host, as Home Assistant works that out for itself.
I am not certain of the last part, but it is true for me.
