Why would you count Rufus and balena etcher not trustworthy? Sounds like you’re to deep in the paranoia, which I completely understand, but gets just impractical “Man yelling at cloud” depending on how deep you are.
dd is just another program too, why trust dd? Linux is just another Program too, why trust Linux? And so on. You can audit every (OSS) Program if you want in theory, but let’s be real, no one does that because time is better spent elsewhere.