Oh; fun!
I'm lucky enough to be experimenting with a new M1 Mac mini, and followed through the prompts (on a kinda autopilot, from setting up my own MacBook) to set it up with FileVault 2 "full-disk encryption", even though this will be a server.
So I found out the hard way, that this then requires (purposely; for security) entering a password _very_ early in the boot process - before it even gets an IP address.
Which also means no remote connection; not via Screen Sharing, or ssh - no headless.
(Note: There is a way to avoid this - for a single boot.)
But; back to the cool part; I rebooted (to apply a software update) before I remembered the above, and a few moments later, while I was trying to debug why I couldn't reach it, the mini (which was indeed headless), started playing the "Find My..." sound effect - that is a nice touch!
