Can you send me the twrp file?
Ted presley told me the steps
Open the rom zip file, and looking in the follow folder:
xiaomi.eu_multi_MI9_9.3.14_v10-9.zip\META-INF\com\google\android
You will find a file name: "updater-script", copy it, paste it somewhere, open it with notepad. In the first line you will see something like this:
getprop("ro.product.device") == "
cepheus" || abort("E3004: This package is for \"cepheus\" devices; this is a \"" + getprop("ro.product.device") + "\".");
Replace the "cepheus" with "xiaomi9", you will have something like this:
getprop("ro.product.device") == "
xiaomi9" || abort("E3004: This package is for \"cepheus\" devices; this is a \"" + getprop("ro.product.device") + "\".");
Close the file, it asks to save, yes, save it.
Afterthat, copy the file back to the zip and replace the original file (recommend using winrar or 7zip instead of the windows explorer).
Done, copy to phone, flash the zip.