net-dialup/ppp-2.4.3-r3 includes the radius plugin, but leaves out its configuration directory (/etc/radiusclient). I'll just copy that over from the source myself, but this is certainly a sub-optimal situation. Ideally (IMHO), ppp would rely on the radiusclient ebuild as a dependency if possible to avoid collisions (as I suggest in bug #92878), but one way or the other, I think this should be fixed.
fixed in ppp-2.4.3-r4. now it installs /etc/radiusclient