Grub is password-protected, what do you do? (Boot from a live distro and chroot into the on-disk one)
I probably own the machine. If the data on the storage is not encrypted, I own that too.
If I don't want to disassemble anything, I just plug in a liveUSB and it's all mine.
If the BIOS has USB/CD boot disabled? I pull the CMOS battery.
If that fails? The google probably knows the BIOS reset sequence for your board and soon so will I.
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Physical security is important too and FDE is not optional. [Even if you have nothing to hide]
If properly secured, physical hacking is not as easy as it used to be.