Well, “a black screen on boot” is unfortunately a common problem what can have tens of different causes. Especially for Nvidia users it’s a can of worms, sadly. It’s hard to document some specific issues.
I updated the common issue with another root cause, which is having an external monitor attached:
For anyone also affected (but “slightly differently”), I recommend to test both F43 Workstation and KDE Live images:
a) If you see the problem on both images, it’s not one of these KDE-specific issues. You can file a bug to RH bugzilla, or create a separate topic in Ask Fedora and hope that somebody can help. Also remember that there’s a troubleshooting → safe graphics mode in the Live image menu before boot, which can help to perform the installation (and then you can hope that some updates fix it).
b) If you see the problem just on the KDE image, and you performed all available workarounds and still doesn’t help, you can file a bug in RH bugzilla, or KDE upstream tracker, or discuss here in this topic, and perhaps people can figure out yet another KDE-specific bug to be documented and fixed.