Xiaomi Mi 8 - Informal firmware (Post linuzzz7 # 80471241)I did not work on this instruction to put HAVOC.
Used the old method with XDA, it turned out.
The method itself, if anyone needs:
1. Clear Data / System / Cache / Dalvik
2. Fix the latest Miui Developer (which beta)
3. boot into the system
4. Customize
5. Boot in TWRP
6. Clear System / Cache / Dalvik
7. Install Havoc + Gapps + Magisk 18 and newer
8. Boot in TWRP
9. Clear Data / Cache / Dalvik
10. boot into the system
Perhaps some items may be superfluous, but on this method works.