grub: terminal_output
16.2.3 terminal_output
----------------------
-- Command: terminal_output [--append|--remove] [terminal1] [terminal2]
...
List or select an output terminal.
With no arguments, list the active and available output terminals.
With '--append', add the named terminals to the list of active
output terminals; all of these will receive output from GRUB.
With '--remove', remove the named terminals from the active list.
With no options but a list of terminal names, make only the listed
terminal names active.
Info Catalog
grub: terminal_input
grub: General commands
grub: terminfo