Surface RT Quad Boot, with 4 different OSes installed in, the impossible boot made possible...

The Surface RT was one of the worst failures done by Microsoft, I owned this device back in 2022 to testing it but unfortunately my touch cover and SD card slot were broken in 2024 (so this is the reason of why I did this), recently I have installed four different OSes: Windows RT 8.1, PostmarketOS Linux, Android 7.1.2 and Windows 10 15035 inside here, this method seems to be very hard but I made it, I also modifed Windows RT 8.1 to install apps since the store was closed already and Windows 10 15035 to have Chinese language that was done by Chinese community since it was originally only completely in English, turning Surface RT less useless, you can have than two different OSes at once and three even four if your device has 64GB space.

The grub loader can load every .efi file, I installed Android first, then installed Windows and finally installed Linux, the bootmgr.efi has to be renamed due to boot partition will boot it in front of any other .efi, Android can only booted from U-Boot, so grub first chainload U-Boot then boot Android via U-Boot, before doing install Windows after installing Android, I have to backup them in after OOBE from to avoid install failure, thanks for PostmarketOS has pre-built images for this device, I can install it easily.