Mi6 Sagit (ULBL, TWRP 3.2.1, Magisk, API2 Mod).
First boot (no clean install, but did a cache/dalvik wipe) went very slow, it took four minutes to boot.
First couldn't find the Sim card and after a minute of closing apps because it keeps crashing, the Sim card was found. Then the apps stopped crashing. After that the Nova launcher crashed too and I was asked what my default launcher should be. Nova launcher.
Apps kept bring slow, and Google sync took ages.
Second boot took less time, but still long. Didn't wait until everything was loaded again. Powered off again and booted again.
The third time and the times after it, it finally booted the way it should be.