If you think that a 3-letter agency is making a concerted effort to tamper with your personal computers, then you basically can't trust anything about your comp

If you think that a 3-letter agency is making a concerted effort to tamper with your personal computers, then you basically can't trust anything about your computers at all, forever. What makes you think that your SSD actually got overwritten? How do you really know that the firmware you flashed actually has the correct signature? Extra hardware could be hidden inside connectors, or packaged into re-labelled chips that look exactly like what you're supposed to find. The only end to it is if you: 1. stop using computers or depending on them to control anything about your life, 2. or build a computer (and all the necessary tools, etc.) entirely from resources which you either already trust or that you circularly prove are trustworthy (you'll have to do this in a totally secure workshop so that you know nobody tampers with your work before it's complete and you've sealed the computer shut), 3. or just give up on having total trust in your computers.