An actual great way to get into ML with a 32bit MCU.
There is a Arduino, I think its a Nano 32 something or another with a built in sound sensor. I use ESP32's and would have to add in a sound module for such a project.
With ML, machine learning, you would create a project that would record in digital, the sound of the doorbell.
Once you got the data model of your doorbell sound it will be a choice of either TensorFlow Lite or Linear Regression, The Nano 32 or a ESP32 can do 32 and 64 bit floating point linear regression. Now, when the sounds come in on the mic, the sound stream can be compared against the trained model and "that a doorbell".
Such a project will teach you a lot.