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1. Copy UltimateRetouch3 Folder To C:\Program Files (x86)\Common Files\Adobe\CEP\extensions
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2. - If you get extension not properly signed at launch:

HKEY_CURRENT_USER/Software/Adobe/CSXS.9 (This can depend on your PS version, it could be CSXS.8 and CSXS.6.)

Apply "PlayerDebugMode" Value 1 and you're done.

Left a regfile that is for CC2019.