XPS 15-9550, BIOS update, black screen

Dell BIOS updated last week and within a few hours the screen began to flash on/off (black screen but backlight of screen still functioning). This flashing display increased in frequency throughout the day until eventually it was flashing non-stop. I tried restarting and even the Dell logo while loading would flash and have lines running through it. This wasn't related to lid position, it is clear video is not working. I plugged the laptop into an external monitor and it worked fine that way. Unfortunately while trying to get my laptop screen to write I disabled first the Nvidia display driver (no change), and then the Intel display driver (after re-enabling Nvidia). That caused any connection to my external monitor to shut off. Now I'm stuck with no way to display anything. On startup the monitor backlight turns on but no Dell symbol appears and I cannot enter any safe mode (or Windows 10 equivalents). Connection to external monitors don't work (monitor acts as though not plugged in). I unplugged CMOS battery for 20 minutes but no change upon putting everything back together. I'm pretty sure it is starting up to the log in screen as eventually the keyboard backlight and caps lock lights turn on, it just seems like any video is completely disabled and I'm out of ideas.