When you say Gamut mapping, are you talking about Tone Mapping?

Tone mapping is highlight roll-off, so affected the brightness/EOTF.
Gamut mapping is as with 'Vivid' mode, and affect the gamut, not the brightness.

Steve

Viewing the Extracted ColourSpace is blanked out on the latest version for me. It doesn't let me see it.

I want to see where the Gamut mapping issues are.

Im sending the TV a RGB signal

I think also another potential issue is that 4:4:4 chroma is processed as 4:2:2 in Vivid.

TV needs to be in Game mode or PC mode to get full 4:4:4.

Sorry, no idea what you mean.
And being 4:2:2 is not really relevant.

Steve

Vivid mode has everything pushed to extreme clipping and color boost.

It's impossible to use that useless picture mode.

Unlock and use the Professional modes. If you encounter any clipping, reduce the contrast and verify with Gray RGB large to check the RGB separation and the clipping charts of your top-end.

RGB Balance always comes out bad in the darker shades. Why does this happen?

Attached file: Gray Ramp Verification

Attached file: Target Colourspace

Impossible to say anything without the pre-calibration profile.
And you can just zip all files into a single zip.

Steve

Pre Cal Profile was done in it's professional mode to see if I can get better results. But same issue in darker shades of grayscal.
Also done with a smaller patchset. Small or big, same issue.

Pre cal profile goes along with the two above zipped files

Attached file: Pre Cal Profile

The profile still shows bad volumetric issues, as visible with the RGB Separation graph for example.
You can also see the same in the 3D graphs when you map the profile to its own extracted colour space.
So there is still some form of gamut mapping going on, which is noticeably worse in the shadows.
(The tangent lines show this.)
As said, try a large Grey Only Quick Profile.
Or possibly a reduced gamut patch set.

Steve

Please only take measurements using Gray + Primary Ramp.

Ensure your TV is configured for HDR; check settings if necessary.

Set Peak Luminance to High, Brightness to Max, and Contrast to 90.

What's best to use 2% or 10% window?
2% is brighter than 10%.

10%

I took a Gray + Primary Ramp in PQ HDR.
LUT still comes out with issues.

Attached file: Sony B8 II - HDR Verify.zip

Edit: The profile is a PQ profile, with clipping.
That will not work.

Also, the RGB Separation is still not good, and any profile that has RGB data will therefore cause issues.
And you can now see the first measured RGB patches (specifically B & G, although the same issues is within R, but harder to see) are really wrong, with a gamut that jumps well outside the rest of the TV's gamut. And that happening near black is not good at all.
That, as well as the bad RGB Separation, is what is causing the near black issues.

Basically, the TV is really bad pre-calibration.
No QD-OLED should have such poor RGB Separation - it really shows the internal TV image processing is bad.
And that bad data is causing a lot of the LUT issues.

I did say to use a Grey Only Large, as that only has three RGB measurement

You could also try raising black, so you get a valid black reading, to see of that helps, as at the moment the black is a null reading, and the first actual colour readings are bad, as stated above, and as you can see on the graphs easily now.
One of the problems of using a low-end probe, but also really poor image processing on the TV.

You may also get better results with a Map Space LUT Generation, or the manual 2-step approach.
Both mean initially calibrating the display to itself, and then mapping into the final target colour space.

Steve