I have finally found a way to fix the Xposed incompatibility with MIUI 9. If the official v88.1 is not working on your device then try this. Take in mind: this modded version of Xposed it's for MIUI 7.9.21 and higher! We can use this version which works perfectly until rovo89 solves the MIUI incompatibility.
arm64-sdk24 (Android 7.0) DOWNLOAD
arm64-sdk25 (Android 7.1) DOWNLOAD
Magisk version will be released soon!
Reboot to recovery
Flash the right xposed
wipe cache and dalvik (Optional)
All credits go to @rovo89