If you want to be able to reboot remotely, and non-interactively (i.e. while you sleep), I (and one other person) created Mandos for this purpose: <https://www.recompile.se/mandos>. It gets the password over the network. If this seems insecure to you, read the FAQ: <https://www.recompile.se/mandos/man/intro.8mandos>
Mandos works with initramfs images created by both initramfs-tools and dracut, and is present in Debian since 2011, so no need to use a third-party package.
I haven't looked deeply into either, but how does this compare to the combination of Clevis and Tang that e.g. Red Hat/Fedora seems to favor?
Good FAQ, clearly stating the weak point of physical access. For a server that threatmodel can work, for a fleet of edge/iot devices in unsecured locations without permanent uptime there is no real solution to be expected without custom silicon logic (like in smartcards) on the soc.
Why is this needed at all? As the decrypted key is in memory before the reboot, can’t it just be written to a know location in memory and have kexec be instructed to read it early on?
How does this compare to: https://docs.redhat.com/en/documentation/red_hat_enterprise_...