I use this app Tracker Control https://github.com/TrackerControl/tracker-control-android to decide what gets internet access. I dont know if it is available on the regular Play apps store.

This or Amy other method will likely render you unable to find your device if lost. So of you still want that feature, you'll need an alternative implementation.

https://docs.quad9.net/Setup_Guides/Android/Android_9%2B_%28Encrypted%29/

now, you have to find some boutique resolver blocking xiaomi, and dunno if it pings it directly by ip (or non dns queries) *(then dns won't help), but that's something i would try first (if it works via dns, your find phone thingy will just ping into aether without response, but find feature also wouldn't work). (i would watch by router logs, if i were that interested (is it one file or myriad of exchanges etc), but you have to know the time of the dump to make sense of thousands of requests in your home network and be proficient to be worth your time)

tbh, sounds like for some reason it just dumps accumulated data each time, so maybe update or some other reset shit (toggling settings back and forth and wait for a day) will help