I’m currently testing this on a galaxy S7 Edge which has a Mali-T880 GPU, according to the device profile, this should have it set to android_high.
I enabled Mobile HDR and set r.tonemapperfilm= 1 in the defaultengine.ini file per these instructions: Post Process Effects on Mobile Platforms | Unreal Engine Documentation
However, nothing seems to work. If I enabled bloom, I get a weird effect on the screen. Like this black and red splotch that flickers as I pan the camera.
Nothing else seems to have any effect. I tried changing the temp to a really weird bright blue, and when I built it and ran it on the device, the scene appeared normal as if no post processing had been applied.
I do have an in-game settings menu, which includes “post processing” but it is set to epic (setting it to low seems to slightly change the brightness of the scene so it is doing something).