The ProgramData location is Adobe-supplied profiles that work with the Camera Raw plug-in for Photoshop and the DNG Converter which is why deleting them had no effect on LR.
LR’s Adobe-supplied profiles are in the Resources folder underneath where the program is installed.
However, it seems like you’re wanting access to third-party or user-supplied profile. A non-Adobe-supplied profiles goes under your Users folder and is shared between LR and PS:
You should not be removing the Adobe-supplied profiles. You should just put the downloaded profile in the folder, above, and it should be found automatically, so no need to ever go through the lens profile list, right? If it is not found automatically then you can find it, once, then set the profile as the default for the particular lens and set the LR defaults for lens profile Setup to Default instead of Auto.
Thanks for the quick response, ssprengel! Your first two lines solved my problem. In my case, the files were in C:\Program Files\Adobe\Adobe Photoshop Lightroom 5.7\Resources\LensProfiles\1.0\Canon.
I think I wasn't as clear as I could have been. The downloaded profiles aren't an issue, aside from two of them not showing up, even when they're in the same folder as the one that does show up. I suspect they were intended for PS, rather than LR, though why they don't work in both is a mystery.
And I agree that LR should find the corresponding lens, if I have the profile in the right folder, but it doesn't. In this case, it's the Samyang/Rokinon 14mm, which doesn't pass any lens data to the camera, so it's not in the EXIF for LR to use in matching it up with the profile. But, it's not a big deal, now that I don't have 150 Canon profiles to scroll through in order to get to the one I need.
Third-party profiles you put into the Adobe location are ignored. Lens profiles are specific to raw or non-raw files and won’t work for both.
If your outside lens profiles aren’t showing up it is either because they are in the wrong place or they are for a format that is different than the current image.
There is a way to hack raw profiles to work with JPGs, by editing them in a text editor and changing the whateverRAW value from True to False.