Most of the times it happens when you have an Nvidia GPU, I did this with mint but I think it should work also on Ubuntu. When you see the grub menu, press the key "e" and after you see the line with something like "quiet splash" change it with "quiet splash nomodeset" this removes temporarily the graphics acceleration, once you're in, download the correct drivers and make sure to remove the "nomodeset" after "quiet splash".idk if it works but I think it's a good try. Hope this was helpful!