FileVault2 command line commands in Mojave?
The command you want is: fdesetup

From its manual page:


  fdesetup(8)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;BSD System Manager's Manual             
  
  NAME
  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;fdesetup -- FileVault configuration tool
  
  SYNOPSIS
  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;fdesetup verb [options]
  
  DESCRIPTION
  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;fdesetup is used to enable or disable FileVault, to list, add, or remove
       enabled FileVault users, and to obtain status about the current state of
       FileVault. Most commands require root access and need to be authenticated
       with either a FileVault password, a personal recovery key (if enabled),
       and in some cases the private key from the installed institutional recov-
       ery key.  Some status related commands can be run from a non-root session.