I'm using a Motorola Moto G5s plus, Android 7.1.1, with Magisk 16.0 in place - and each version of f2fsfix is working (2018.10.9, 2018.9.2 and 2018.3.6).
But when upgrading to Magisk 17.x (no matter if 17.0, 17.1, 17.2) I always get following error message showing up in Magisk Log Window:
mount...