[devit]

The normal non-Google way is to configure initramfs to start an SSH server on a non-default port, and then you log in (from your secure workstation with a dedicated public/private key, of course) and use systemd-tty-ask-password-agent to enter the disk encryption key.

You can then monitor whether your service is up, and if you get a notification that it's down use the hosting service's management interface to reboot the machine/VM and then do the SSH thing.