Deliverable computer security is something which does _NOT_ exist. If somebody is telling you otherwise, they are trying to sell you something.
Less worse scenario: you need to strip down software (including the SDK) and hardware to the bear minimum, and to aim for excrutiating simplicity still able to do a good enough job (this is currently mostly denied by the "planned obsolescence" and "overkill complexity" from Big Tech or brain damaged "standards/SDK"). Maybe, then, and I say maybe, you may have a little chance, but usually that chip(CPU) you are using is full of backdoors (or convenient bugs) anyway.