RRF has PID and First-Order Plus Delay Time (FOPDT). According to my basic understanding, FOPDT needs to be tuned just like PID to represent the physical characteristics of the systems but uses a different feedback loop approach.
Klipper has an experimental branch for FOPDT as well. See Experiment with "First Order Plus Delay Time" (FOPDT) temperature tracking
Edit: See Tuning the heater temperature control | Duet3D Documentation