It fixes slow motion by using the libraries containing Oxygen OS Nougat Camera Hal. This will solve the force close when attempting to use slow motion with Google Camera, Snap Camera, Open Camera and similar.
Every Oreo/Pie-based Rom (including Oxygen OS of course).
3liteking148 is the one who made this possible.
MarcAnt01 updated to new Magisk installer, added device check and other minor stuff.