> Curiously I got it into a weird mode where artifacts from a corrupted framebuffer in DOS were persistent on screen as a faint ghost image after booting into Linux even when cycling the power for a short duration. I have no idea how that could happen.

This is most definitely a hardware issue with your display, not the frame buffer. What you describe would require alpha blending in software and couldn’t just “happen” with a linear array of corrupted bytes; it would require intentionality.