Intercepts isTypeSupported() calls by YouTube and lies about HDR support being available.

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If this has no effect on yours, please edit the code of the script by removing the // on this line:

//console.log('testing for: '+ type);

Then, when you load a video, the script will dump out a list of all the different codecs YouTube is checking for to the Web Console.

Reference: https://developer.mozilla.org/docs/Tools/Web_Console

I think the interesting ones will contain eotf so you can filter the Web Console on that as a first approximation.