Thanks for your patience so far.
We have now received feedback from our specialists that we are happy to share with you:
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This version (TPM211EA_R.001.002.092.000) indeed exists and can be used on an OLED806, assuming that it's a PKG file (otherwise, a downgrade will be rejected by the TV, of course).
However, it will not solve the AmbiLight behavior since the behavior is rooted in the FRC firmware, which will not be touched during the downgrade.
We are not at liberty to tell whether user xyz in the forum has been provided this version from our end due to GDPR reasons.
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With this in mind, we are unable to provide you with this version. Nor can we offer you a solution, because this is not a defect, but normal behavior of the TV and a downgrade will not offer a solution.
Hoping to have informed you enough with this, I wish you a nice day.