Comment by bri3d

Low end and most open source stuff will use a PID inner loop for “fast path” control (stabilization) and either a second PID loop or something a little better (Kalman filter etc) for the slow path (position / path hold).

Higher end stuff will use a ton of inputs (visual odometry, binocular vision, lidar, range finding, etc) fused into some kind of proprietary blended algorithm that you could probably call an MPC.

RL is pretty cutting edge, especially for fast path motor control; there are a lot of university competitions for drone control that lead to a lot of papers and projects in the space (some promising) but most commercial stuff has not adopted this yet, certainly not at the low end.