In e,g,, /etc/grub.d/10_linux

with lines like

ubuntu_recovery="0"

instead of

: ${ubuntu_recovery="0"}

and

if [ -x /lib/recovery-mode/recovery-menu ]; then
    GRUB_CMDLINE_LINUX_RECOVERY=recovery
else
    GRUB_CMDLINE_LINUX_RECOVERY=single
fi

instead of

if [ -x /lib/recovery-mode/recovery-menu ]; then
    GRUB_CMDLINE_LINUX_RECOVERY="recovery $GRUB_CMDLINE_LINUX_RECOVERY"
else
    GRUB_CMDLINE_LINUX_RECOVERY="single $GRUB_CMDLINE_LINUX_RECOVERY"
fi

at

if [ "$ubuntu_recovery" = 1 ]; then
    GRUB_CMDLINE_LINUX_RECOVERY="$GRUB_CMDLINE_LINUX_RECOVERY nomodeset"
fi

it's no wonder users have no simple way of adding nomodeset themselves,
from the environment, without editing the file.