Why would we leave the battery out? Some folk fall for the "I want to save the battery" or other tropes.
The D key seems to work as per https://www.dell.com/support/article/us/en/19/sln131497/how-do-i-run-diagnostics-on-a-dell-laptop-lcd-?lang=en but you need to go deeper.
Does the Dell splash screen or BIOS show? I'd be trying to get to the Dell BIOS next.
Recently i upgraded to w10 on my Dell XPS M1530 and my computer was running fine on it so i was playing gmod on it and i had forgotten to put the battery into it. After that, the charger was unplugged so after restarting it came up with the troubleshoot screen so i did a reset that would delete everything exept my personal files but that got stuck on 8% and wouldn't go any further. So i had to restrore the system to the last working point so i left it to do that for about 4 hours and it told me to restart and my computer doesnt restart correctly so i let it restart and turned it on myself and it came up with the troubleshoot screen. I tried starting in safe mode and it made me restart the computer and after i turned it on it just came up with a purple loading screen that just turned to black eventually. Now it just comes up with a black screen and i cant get past that point. I can do On+D but that doesn't do anything but flash colours
(btw i have tried hard reset but it didn't do anything)

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