The answer is "it depends".
I had a 2005 Outback base that I put an aftermarket head unit into several years ago. Among other things, that little project led me down several rabbit holes and cow paths regarding steering wheel control (SWC) connections and adapters.
I was fortunate in that the steering wheel I robbed from a 2009-ish Forester had a resistance ladder-type connection for the audio controls. (Pressing a particular button changes the voltage input to a wire vs sending any kind of electronically-coded pulse signal.)
Doubly fortunate in that the head unit I was using at the time had the ability to program a specific button to radio feature (volume up, volume down, tune up, etc).
I am attaching the wiring diagram for the 2018 Forester that shows the SCW connections. The good news (hopefully) is that if I read it correctly, the 2018 Forester still uses a resistor ladder to create the different signals.
--HOWEVER--
Intercepting the SWC wiring at the base of the steering wheel column wiring was an adventure. Since I had (not unfounded) concerns about modifying any factory wiring, I had to rob a couple of connectors from the junkyard to break out the SWC wire and feed it into the custom plug that fit in the back of my head unit. Not difficult, just tedious.
The Maestro device has the advantage of being plug-and-play. If you lack the skills or patience to modify your factory wiring (or just plain don't want to), the Maestro device is a good alternative.
As for the "connection to parking brake", that's a wire that is to be hooked up and the proper connection (and thus input signal) is made so that certain features are only available when the parking brake is on (and also the car is in park, not being driven). Keeps someone from watching videos while driving down the road (in theory).
Hope this helps, and good luck!
Glenn
