/etc/fstab to mount a few external volumes at boot time (using a UUID= line). That makes them available at boot before anyone is logged in and thus they can be used for certain services.
This is easy enough and it works. It is also essential because there is no way to let LaunchDaemons wait until disk arbitration is up and running for volumes mounted in /Volumes. It also enables Time Machine to operate continuously, also when nobody is logged in. Which is very useful for a 'server' Mac (e.g. running Server.app for Open Directory and other open source services).
What I haven't done yet is try to do this with an encrypted volume. I was wondering if there is a way to have the external volume encrypted and still mount it before anyone is logged in.
The machine is a late 2018 Mac mini. It has a T2 chip so maybe I can use the security commands to tell the Mac about the credentials for the external volume.
I am using macOS Mojave but expect to be upgrading to Catalina.