i tried to get kde plasma on my fedora, when i booted it up there was just a black screen. i couldn't type any commands either, it was toast
thankfully i've got windows dual booted because i'm a filthy 
who uses it for vr games. unfortunately windows doesn't let me see my linux drive's files so all of my personal files are unrecoverable.
thankfully i think the most i had on my computer was my music (yt-dlp is so easy i can get it all back in 30 minutes tops) and a few files from some project i was working on, sucks but not worth spending hours troubleshooting. oh well.
on the bright side, i'm RETVRN-ing to my old reliable, linux mint with xfce. i'll miss hot corner and the other niceties that gnome has but xfce will be a bit more comfortable for me.
If you can boot windows, that means you can get past the bootloader, which means it's actually running linux before the screen goes black. with that in mind:
do yoy have extra kernels you can boot into? I use Debian, and they automatically maintain a few boot options including an older kernel and a "rescue mode". But that might just be debian for all i know
any change when you plug your monitor into your PC motherboard's graphics port instesd of the GPU?
can you switch between TTYs once the os boots and the screen goes black?
Sometimes graphics issues like this just means the GPU isn't working, which 2 should diagnose. But given that it happened when you tried to switch DEs, my bet is on either the Display Manager or the window server (x or wayland) failing, which 3 should get you around, and then you can proceed to diagnose and unbork it from the terminal