https://www.dedoimedo.com/computers/grub-hd-scaling-resolution.html
edit /etc/default/grub
GRUB_DEFAULT=0
GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=10
GRUB_DISTRIBUTOR=lsb_release -i -s 2> /dev/null || echo Debian
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""
GRUB_GFXMODE=640x480 GRUB_GFXPAYLOAD=keep GRUB_TERMINAL=gfxterm