Every image I've tried to use the new masking Select Subject/ Select Sky masks on I get the same error:
"No Subject Detected: Couldn't find a subject to select. There might not be prominent objects in the photo."
But I've tried this on so many images at this point, ones with very clear, blue skies with fluffy clouds, or clear human subjects and it never finds anything to mask. I've tried this on raw images and jpeg's just to see if that helped.
Please post your System Information as Lightroom Classic (LrC) reports it. In LrC click on Help, then System Info, then Copy. Paste that information into a reply. Please present all information from first line down to and including Plug-in Info. Info after Plug-in info can be cut as that is just so much dead space to us non-Techs.