In my case, OTA didn't find any update. I updated from my previuos xiaomi.eu miui 10 stable, with TWRP as usual.
Here my steps.
- updated twrp from fastboot with latest 3.3.1-42 Mauronofrio
- rebooted to miui, then copied miui 11 mi9 stable to memory phone, from my pc by usb as usual
- booted to...