After I start OpenSUSE, su takes an extremely long time to run. Basically, I run su and enter my root password, and then just sits there frozen for a minute, before I finally get the prompt. I try to run kdesu, it just freezes after I enter my root password, and then eventually quits. Half an hour or so after booting, su fixes itself and becomes instant.
To make the picture of what you are doing a bit more understandable for others, Where do you use that su command? I assume that not only openSUSE is started, but that you log in also (else there is no place to enter the su command), but it is not clear if you loged in in the CLI (on the console), or that you did a graphical login (and when yes in what desktop) and then started a terminal emulator (again which one).
Yes, I log into KDE Plasma, and then I run su in Yakuake.
How did you upgrade?
zypper dup
It takes less than 1 second here.
Suggestion:
- Open a konsole
- Run “top” in that konsole.
- Does the system seem to be looping? Is the load average bad?
- Now try your “su” (while “top” is still running.
- Does something now seem to be looping. Has the load average jumped up?
This seems to have stopped happening after an update.
Sometimes things solve themselves 
Thanks for reporting this.
Now the problem seems to be back, and there was nothing heavy running.
Well, back to post #6 above I would assume.
I don’t see anything heavy happening in top while su is running. As for load average, it might increase a little, but it’s hard to tell since it’s constantly varying anyway, and it’s just an average. If it increases, it’s not by much.