My advice is, stick to your odroid C2 and ATV until new kernel available for s9XX or something come up with HDMI 2.1.
I was under the impression the C2 cannot do HDR. That it was a hardware thing. Wrong impression?
Regarding the ATV, I'm aware of MrMC, but the issue is that the ATV doesn't pass through Atmos. I think that issue is at the firmware or OS level.