Did you try to flash a really old MIUI version on Android 9 to see if it was less secure and allow to retrieve Widevine?
You can find some old links here: https://mirom.ezbox.idv.tw/en/phone/raphael/roms-eea-stable/
Here is a drm.txt
I did a persist partition restore from a dump I'm sure it was L1, but still the same.
Xiaomi Mi 9 (21.4.21)
EDIT: I've just looked into /vendor/firmware_mnt/image, I don't have widevine.mdt but I have widevine.mbn file
Hi,
Xiaomi just updated the devices list, Redmi 3 is now available with its China ROM : http://en.miui.com/download-298.html
Now waiting for a Global ROM...