I can't speak to Tidal but I don't think it will work that way for Apple Music. I tried that with my setup as you suggested and only seem to be able to get upmixes. It could be that my TV doesn't support Atmos through it's HDMI eARC output but I am fairly certain I read somewhere you need to have an Apple TV 4K box, which is how I actually am able to get Atmos streaming. You may be also able to use a Mac computer, not sure as I don't have one.If the 'streamer' is a networked smart TV that has a Tidal or Apple app, and using HDMI ARC from TV to AVR, does that suffice for streaming mch?
Again, the results may be different for Tidal but I don't have a subscription to that so I can't check.