What I did (Through fastboot, of course):
1) Fresh install of MIUI 10.3.1.0 (That was not necessary for this ROM, but I had unrelated problems. But so you know it really is of the factory state)
2) Flashing official (From Xiaomi) dummy.img on partition "antirbpass".
3) Flashing official TWRP 220.127.116.11 on partition "recovery".
4) When flashing build 20190527PIEFW through TWRP, I got Error 7. The install was aborted.
Surely the latest Global Stable MIUI (10.3.1.0 as of writing) has the PIEFW, right? Weirdly, AOSIP (only OREOFW) installed fine.