Ask HN: How do you trust that your personal machine is not compromised?

For the rest, I run a pretty esoteric setup (compiled-from-source custom configured linux kernel with no binary blobs; all software compiled from source, with no exceptions; aggressive, burdonsome-to-me privilege separation; chroots and VMs for various degrees of potential threat; etc). I have no illusions that it is perfectly safe. What I am comfortable with is that, in order to compromise me, you would have to know a lot about what I run and how I run it. I believe that I would have to be nearly individually targeted to extract any useful data from my machine, and that I am not nearly a valuable enough target for anyone to do so. I think you would have to be a state-level actor or someone with similar capabilities to compromise me, and none of them would care enough.

My security paranoia stems from extremely sensitive work I did as a lawyer long ago, but I am now so used to it that I carry on as a scientist, even though my current work is not nearly so sensitive (if at all). I give up a lot of convenience and some functionality to operate this way, so it is not for everyone. I am not an adversary to anyone, so outside state actors surely don't care about me. And my own government can just get a warrant and knock on my door, so they don't care about me either.

Embedded device firmware besides the bios is probably my main vulnerability, but if you're successfully getting at me through my hard drives or mouse, then I was surely an incidental rather than actual target.

Mostly the same basics as you. The document you linked is a good starting point.

I'd add extensive use of virtualisation and sandboxing. I run less and less software as native, installed applications on any device I use personally or professionally. Instead it tends to run inside things like VMs or Docker containers or cloud-hosted platforms now.

My basic policy is to try and make every device and installed application expendable/replaceable in case anything breaks or gets compromised and then focus on the data. I apply the principle of least privilege for access to any sensitive data, try to keep all important data in standardised formats and avoid lock-in effects as much as reasonably possible, and keep good back-ups under my own control with the ability to redeploy/restore anything quickly and as automatically as possible.

OS/app level: occasional AV scans, though I don't trust clamav as much as I trust Windows antivirus.

I should really properly set up secure boot on my desktop to make rootkits harder to install, but Linux and secure boot are just too much of a kludge.

If you assume every device you use is compromised, how can you possibly use any encryption?