There's work being done on making Blockly (the software that creates App Inventor's blocks-based coding editor) accessible to screen readers, but it's still got a ways to go! Last I heard (Oct 2019) it was still in the testing phases at the University of North Texas.
Unfortunately, App Inventor is even a little bit further behind than that because they're running a version of Blockly that's a few years old.
So in short, no. At the moment there's not really way to make App Inventor screen-reader accessible 