[LG G6 Questions and Answers] Ghostface009:
Interesting, Smart question.

before answering your question let me point out that if you like to settle with inaccurate/incorrect answers then just settle with the answer above or stuff you find after googling that question.

I also like to point out the reason why this question is smart and interesting mainly because for some reason, bit depth related questions are not answered properly and there is a huge misunderstanding because of false information and details that you get on the internet or false advertising as some manufacturers falsely-advertised their panels as "10 Bit displays" (esp. if you're buying a monitor, be aware of these scams , pay attention to the details like the model and do a dedicated research on the subject)

Let's get into your question

Oh man, op, I'll be honest with you, you got yourself in a deep, deep vortex because the answer to that question packs a lot of information, I hope you read everything patiently because I didn't write this article-like long reply for nothing but educational purposes :)

First of all there is no such thing as "10/8 bit display" or "10/8 bit panel", 10 bit display likely doesn't exist and 8 bit display is atari content, 10 bit display is what you meant/referred to is likely the "bits per channel" which isn't the number you're looking for, as some panels could have 8bpc, but can have more subpixels which result in higher bitdepth than 24 bit (like rgbw, 8 bits for channel in rgbw allows true 32bit panel resulting in more colors/shades generated due to additional channel and additional data or 8 bits stored for that channel, plus the color combining by the usage of the additional subpixel to control each shade, in this case adjusting the saturation of the white subpixel, in a colored/white & black gradient testing these panels will subjectively and objectively give you the same color output and the same wavelengths) channels here stands for the subpixel, the actual bit depth of the display is the bit depth of it's pixel, which is 3 (likely 3, because many pixels use RGB color palettes/segments, but can differ as mentioned above) x bits per channel

So the formula of the panel's bit depth is generally like this :

No. Of colored subpixels X no. of bits per channel(subpixel or pixel)

Example: a given panel has RGB component, for each channel (subpixel) it stores 8 bits, the total bit depth of the display equals that number x 3 which equals 24 bit, also known as true color, more informations about the subject can be found here

https://en.m.wikipedia.org/wiki/Color_depth

(Notice the "do not confuse with bpc" line, also notice that higher bitdepth than 24 bit or "true color" is also known as "deep color")

But manufacturers, oh they beg to differ, and will always publish the bit per channel instead of the actual bitdepth of the display just because they feel that their rgb display is unique for achieving 30 bit depth or bit depths more than 24 without the need for extra subpixel and honestly they have all the right to do it.

What you are looking for: whether LG G6/Sony xperia xz premium/galaxy note 7/galaxy s8 have 30/32 bit displays.

The answer: not definitive.

There is no definitive answer for your question, there aren't any websites on the internet who measure the actual output by determining each color's wavelength by using a spectrophotometer to determine that there are actual different shades in a gradient/artifact testing, plus spectrophotometers are expensive and not anyone is able to get an accurate tool.

Add the fact that standards like HDR by the UHD alliance or Dolby vision aren't trustworthy at all, many displays had bit depth more than 24 and had amazing contrast ratios, yet they didn't have the hdr standard because they are older than the standard itself, and many panels are given HDR standards or dolby vision, despite not having deep color (30 bit or more) most likely, these smartphones mentioned above, because all of them are listed to have "24 bit " instead of "30 bit" color on websites like gsmarena and devicespecifications and because deep color is really expensive, if you want deep color start searching from laptops and don't go below

How to test:

If you're lazy like most of us humans, grab these videos

https://drive.google.com/file/d/0B68jIlCvW85gWFp0NVUwTFdTNFE/view

Extract them and run them both, see the difference in gradient like stepping in the lower side and no stepping in the upperside of both vids? Cool, enjoy your deep color panel

Also on how to make yourself a test without getting wavelength detectors/spectrophotometer (for devs and designers):

Do a gradient testing by making a .png, one for deep color, consisting of many rows side by side of close of sequential colors/grey tones grabbed from the 30bit colorspace and another one for 24 bit in the same way, take these .pngs and make an mp4 out of them or just place them one atop of another, voila! You made the test yourself

I hope you have been educated and benefited by this response, but I'd like to hear a response from you too after you test the phone yourself :)