Mantine now supports transformation in forms (https://mantine.dev/form/values/#transformvalues).

You can easily substitute values like that :

const form = useForm({
    initialValues: {
        status: 0,
    },
    transformValues: (values) => ({
        status: Number(values.status) || 0,
    }),
});

<NativeSelect
    description="Status"
    data={["0","1","2"]}
    {...form.getInputProps('status')}
/>