According to this old bit of documentation (https://android-developers.googleblog.com/2013/05/handling-p...), the usual way of intercepting call requests should already handle emergency calls ("Note that the system broadcasts NEW_OUTGOING_CALL only for numbers that are not associated with core dialing capabilities such as emergency numbers."), so it'd be interesting to know what went wrong in this case (and why only on Android 10 and newer), but until then it's hard to say more and it's all just speculation…