

Other options are LUKS with Tang and Clevis, or LUKS with SSH and Dropbear.
Sorry, I have no details.
Edit: Tang/Clevis are local software and a network server that provide keys. If stolen, won’t boot.
SSH and Dropbear make it so you can login to provide keys.
No. They can just leave. Anytime one can walk away, it is wrong to destroy or kill.
They can then prevent us from leaving.