I've a Xiaomi phone on which twice appeared obviously debug/hello-world notifications (something like "testtest111") from apps I've never seen or installed. Then another time all Xiaomi phones of close relatives started getting these cheap, spammy ads for Android games in the notifications, this time from some obscure system app: had to look up on reddit that there are settings that disable this specific behavior.
The degree to which I don't own my own device is insane.
The degree to which I don't own my own device is insane.