A long time ago, I built my own crashcart adapter with a raspberry pi and a teensy to do something similar. I would sometimes get weird mdadm errors that would hang the boot process and other times, a reboot or power loss wouldn't actually cause the PC to boot back up. The teensy did USB HID emulation for keyboard inputs. I added the ability to push the power button with a fet and some resistors. I had a cheap VGA to composite adapter going into a USB composite capture device so I could at least get screenshots for any weird boot messages. I built a small webpage using flask to display the screenshot, allow for text input, control inputs, and to push the power button. It was a lot of fun building but a basement flood completely wrecked it. Server was sitting on a 6in platform but the crashcart had fallen off the top of the case and was laying on the ground. Oops.

FYI your decryption key can be MITMed by anyone with physical access to the system. Encrypted drives on a remote server doesn't make sense in practice. Just use dm-verity.

This has been a "need" for a long time for home users with FDE. The go-to software solution for Linux has been:

https://github.com/gsauthof/dracut-sshd

I'm vaguely reminded of some of the third party disk encryption/preboot management utilities that exist in the Windows space that leverage similar technology. Authentication is done against an online source, and only then is the key sent back to the local machine to unlock the disk. The Bitlocker key is kept nowhere near the local TPM.

I've only seen it on some paranoid-level devices in industry (typically devices handling biometric identity verification services).

IIRC this one is a Linux image that boots up, unlocks the normal Bitlocker partition via whatever mechanism you need, then hands control back to the Windows bootloader to continue onwards.

https://winmagic.com/en/products/full-disk-encryption-for-wi...