How to handle “outside” click on Dialog (Modal)?

disableBackdropClick will not work in Material UI v5.

Dialog API (next)

You can use code from the migration guide to handle each closing source manually with the onClose prop by detecting the source of the closing event.

<Dialog onClose={handleClose} />

And use the handler to stop it

const handleClose = (event, reason) => {
    if (reason && reason == "backdropClick") 
        return;
    myCloseModal();
}