Isn’t rescaling usually done by the display driver? I am fairly certain this is the case for external displays. Are laptop displays any different?
Edit: with “display driver” I mean the hardware chip behind the display panel, dedicated to converting a video signal to the electrical signals necessary to turn on the individual pixels.
Can you see at least GRUB, or nothing at all?
If you can see GRUB I would try booting with the “nosplash” kernel option, which causes video drivers to be loaded later.
This is a temporary fix, as it might cause other issues, but if it makes the screen work it will be a step in the right direction.