GRUB and installer invisible on serial console

[Ricardo Wurmus]

Hi Guix,

I just wanted to install Guix System on a server where I currently only
have remote access via serial console — and which happens to have a Guix
USB stick stuck in its USB port.  I can see the system’s UEFI output and
see that it boots from USB, but “Welcome to GRUB!” is the very last
thing I see.  There is no further output.

Our GRUB is using fancy graphics, so I wonder if that means that it has
switched to a mode that I simply can’t see over my serial connection.

Is there a way to make it start GRUB in text mode — and stay in text
mode throughout the installation?

--
Ricardo