So my home router, all my iot devices attached to it from printers to projectors, not to mention custom stacks like Lutron. BLE based locks, car key fobs.

All of these technically could have zero day vulnerabilities and people/companies who made it don't have the resources to buy 20000$ of tokens to go debug them... Maybe they don't care but if they do, what if they can't afford such models or get access in time.

I would like to know how can someone like me defend against them?