I just upgraded my newly installed KDE Plasma and now I am stuck on Memtest forever. Help anyone? I can't even exit out of this everytime I do It starts again.

Looks like either your bootloader somehow got corrupted, or your disks got reordered.

Grub default fucked up?

Try hitting escape or arrow up/down on boot. When the grub menu comes up, select advanced and then the most recent non fallback kernel. Hope that helps.

I rebooted the pc and installed KDE all over again. Now it's fine.
I think what I did wrong was that after the installation I started the system upgrade of about 1.5gb. And at some point it looked like it got stuck so I forced turn off the pc and then that happened. So never interrupt a sys upgrade i guess. But thanks for your comments :)

@unicorndev I think that's the general rule for all OS's 😅