Every 6 months or so I go looking for a solution to this problem and still haven’t found one.
When my phone (Pixel 7) is connected to my car by bluetooth, the phone itself will not make any notification sounds. It is attempting to send all notification sounds to the car. The problem is, if I am currently not listening to any media and the head unit is off, I will not hear anything at all. The only possible way to hear it, is to have the head unit on and set to bluetooth input whether or not I’m listening to anything. This was not always the case. I think it changed after Android 13 was released but I’m not 100% sure.
This has been a problem in Android since about Nougat, if I remember right.
How it chooses to route notifications is inconsistent, and can vary based on the type of Bluetooth connection.
I’m not sure what the answer is, but it’s pretty annoying to not be able to dictate exactly how it routes notification/alarm sounds.