I've installed "Magisk-v17.0" with this method:
a) (re)installation "MagiskManager-v5.9.1(139).apk"
b) from Magisk Manager download "Magisk-v17.0.zip" on folder "Download"
c) on folder "Download" copy "Magisk-uninstaller-20180901.zip" (for any problems...)
d) reboot on recory mode
c) from recovery clear cache and dalvik cache
d) search folder "Download" and sweep on Magisk-v17.0.zip
c) reboot system
Found this files on
https://forum.xda-developers.com/
tested on MI MIX 2, ROM MIUI 10 by xiaomi.eu 8.9.13 weekly