Sailfish has some proprietary stuff to deal with the Android & Sony as well as Qt being Qt. Much of their software is open source—& collaborative with translations & forums for feedback. Out of the box, you on Sailfish you get root support which lets you actually be the device owner. You are allowed to install whatever software from wherever you want… things Android no longer is. It’s not a flawless platform, but Android in practice gives you so, so little control over your actual device.