The baremetal means not using linux or some OS.
Build with scratch to alls. One of the exception I believe VideoCore4 has such an OS on firmware or something.
Requirement
Raspberry Pi Zero W or such devices.
Ubuntu (latest)
Arm compiler sudo apt install gcc-arm-none-eabi
Sample screenshots(I strongly using OBS with using USB-HDMI capture (not expensive)
GPU Driver of the RaspberryPi Zero W V3D Triangle with perspective correct texture.