Drawing to a Bitmap backend docs, sample?

[MihaMarkic]

Let's say I want to draw everything without Skia (or any other provided library) to a custom Bitmap - window and its content. Let's say Bitmap is a System.Drawing.Bitmap. where I have methods like DrawLine, DrawText etc.
It'd be wonderful if there was a sample, but I don't think there is, or? Perhaps there is a documentation of higher view on how drawing is orchestrated. Or perhaps just hints :)
It's complex just by looking at sources. TIA

[MihaMarkic]

Checking out LinuxFrameBuffer now as it feels most similar