I noticed that the internal player can’t play many files at correct aspect ratio, eg you have wider mkv/mp4 videos stretched to 16:9. Image format options don’t change anything. I’ve tested this on few downgraded firmwares available for download here with no luck.
However I found hope. There are DolbyVision-enabled builds of KODI on kodinerds dot net (for our TVs the armeabi-v7a is correct version). Either KODI 19.4 and 20.0-alpha work just fine in my testing.
Few settings i suggest turning on (you might need to switch settings to expert mode at the bottom of the screen):
Disable picture-in-picture so you could change some setting in the tv’s built in menu while
Enable all the eAC3/AC3/DTS passthroughs – tv will do all the decoding of picture and audio then (including Atmos)
You might find that it shows the screen is 1080p and not 4K – doesn’t matter for the videos, they’re decoded and displayed in hardware, I tested this with some 4K test patterns – it’s not downscaled.
With all that you gain flawless MKV/MP4 HDR10/HDR10+/DolbyVision playback, with subtitles that you can make dimmer, so they won’t burn your eyes like on the built-in player.
I don’t know how well it works with external amplituners, I only use the TV speakers.
Hope some of you will find that useful :)
Anyway – this is my last Philips TV – they are just unable to provide good quality firmwares and ambilight alone is not worth the hassle.