https://www.rockauto.com/en/catalog/hyundai,2017,elantra,2.0l+l4,3393930,brake+&+wheel+hub,drum+brake+self+adjuster+repair+kit,1904
RA shows self adjusters , which have a different catalog # for left and right .
I always considered they worked every time you backed up & applied the brakes .
When my wife started driving FWD vehicles , I figured the car would need front tires and pads every 30,000 miles and rear tires and brakes every 60,000 miles .
Either the brakes are getting better or she is driving better . Our 2015 Chevy Sonic has a little over 60,000 miles on it and still the original brakes . She is on the first set of replacement tires .
I never replace discs or drums unless they are thin or grooved . When I need to do a brake job on it , I hope it will not need discs or drums .
As far as the OP , I would not worry about the rear brakes , unless you observe , hear or feel something out of the ordinary .