I see nothing in the options to return full scrollbar functionality, and it is vexing that many applications do have regular scrollbars, and some, or at least Nautilus 126.96.36.199, do not. So how do we fix it. There was a brief discussion at superuser.com in which one person totally missed the point regarding why this is a problem and a couple suggestions were given, neither of which seemed complete. This is how I restored scrollbar functionality, based on the guidance at superuser:
sudo apt-get remove overlay-scrollbar
sudo apt-get autoremove --purge liboverlay-scrollbar-*
echo "export LIBOVERLAY_SCROLLBAR=0" > /etc/X11/Xsession.d/80overlayscrollbars
People trying to do this will likely want to escape the asterisk in the second line. It is not clear to me whether one really needs the first line given the second, but this worked.
My remaining question is why would the Gnome team reduce the scrollbar functionality without providing users with a clear-cut way to revert to full scrollbar functionality? If some prefer this behavior, which seems reasonable, then there should be an option somewhere within Gnome or within individual applications.