The notify when smart app is still available in the marketplace.
Smart home monitor does not yet have any way of monitoring whether locks are locked/unlocked. Presumably that will be added in the future it’s a pretty glaring omission for a security app.
But if you go under custom notifications you should be able to set one up for a contact sensor. I’m using two, one on a linen closet door that has the cleaning supplies and one on the front gate.
I see @smart and I crossposted. If you need the exact steps on getting into setting up a custom notification, I just pulled screenshots for that yesterday for someone who wanted to set up notification off of a temperature sensor change. The Initial steps should be the same just in case you need those.