I am having a2 lite, and I am also looking for MIUI 9 as I miss some inbuilt features like FM, call recorder, etc etc. But I am happy with phone though.
However, I am facing one severe issue which is I get NO notifications tones for whatsapp, email, sms, and other apps. If I restart phone again it start ringing but just for a while than again it goes off. Please note, I use custom notification for whatsapp groups, personal and some people, but I dont think that should be the problem. I was doing that in my earlier redmi prime2 phone and it was working fine.
Also, I get calls even whatsapp calls, it rings perfectly just no tones for messages or notifications. So please someone help me onto this.