After spending several exasperation days trying to get kde to run via "startx", I was informed that I needed to have this in the "~/.xinitrc" file
exec ck-launch-session startplasma-x11
There is no mention of this on the FreeBSD https://www.freebsd.org/doc/handbook/x11-wm.html site. I think that the page should be updated with this:
The startkde script has been replaced by the native executables startplasma-x11 and startplasma-wayland in 5.17.
The ~/.xinitrc file should contain:
exec ck-launch-session startplasma-x11kde