GRUB_CMDLINE_LINUX_DEFAULT="video=efifb fbcon=rotate_all:1 quiet" GRUB_CMDLINE_LINUX="video=efifb fbcon=rotate_all:1 quiet splash noautomount" GRUB_GFXMODE=1200x1920x32
( see here: https://www.reddit.com/r/GPDPocket/comments/9sl9sp/grub_land... )
More super-handy GPD patches https://github.com/stockmind/gpd-pocket-ubuntu-respin
(Note: a lot of this is not needed anymore and mainlined into Ubuntu 20, Linux Mint 20, etc.)