In a decade of Bitcoin's existence and with billions of dollars at play. No one has been hacked through hardware backdoor installed in brand new computer hardware. I think you're being over-paranoid.
Not if your threat model is very serious or you're wanted by government (just like Edward Snowden)
But on normal scenario, i'd agree.
B
right, but if you use that old equipment that Libreboot will run on with it's fully free software/open source firmware, then you're still susceptible to CPU microcode flaws that are no longer fixed for those old EOL'ed hardware platforms.
Which is more dangerous since the flaws is revealed in detail, since more people could breach your computer.