Since the only other binexp I’ve ever done was the simple buffer overflow in Safe, this root has been a wild ride and intense learning experience. But after reading through countless articles about the relevant internals of glibc and exploitation techniques, trying to reproduce them, and failing a lot, I managed to root this beast 
root@player2:/#
Thank you @MrR3boot and @b14ckh34rt for this great box, and special thanks to @will135 and FizzBuzz101 (from the discord) for the recommendations on where to start reading about things