Thanks! This annoyed me to death!
I'm just on here to say that I'm also having this issue on LR CC, Wacom tablet and pen (Intuos) on a desktop (Windows 10) - all current versions/updates. that doesn't have a touchscreen. It only happens when I'm using the pen (not fingers on the touchpad) - when I put the pen's cursor into one of the boxes to input a number on a setting, the onscreen keyboard pops up. Every.Single.Time. It only happens in LR and when I use the pen cursor. It has happened a few times when I'm actually editing with the pen on a photo, as well. I searched for this issue and your post is the only one I could find, so thank you for bringing it up so long ago. Hopefully if anyone else is dealing with this, Adobe will figure out a bug fix. In the meantime, I will try your fix. I have tried disabling it through the recommended settings that I found on other help sites and the onscreen keyboard was already disabled in all of those settings.
Update: The fix did not work for me. The OSK is still popping up in LR.