[tadfisher]

> is it reasonable for tesla to lock you out of the app or software updates if the software hash doesn't match what they provide ?

Of course, and I don't think anyone here is arguing against that.

> would it be okay for them to void the warranty if you run software they didn't provide ?

There are laws governing this exact thing (in the US it's the Magnuson–Moss Warranty Act), and in general Tesla would have to prove your unauthorized modification caused the failure which you're claiming under warranty.