Recently transparency in konsole has not been working. It says in the setting “Konsole was started before desktop effects were enabled. You need to restart Konsole to see transparent background.”
Restarting konsole doesn’t work either.
Sometimes it is worth searching/reading the forum. This question was answered a couple of days ago.
https://forums.opensuse.org/showthread.php/519809-Konsole-quot-background-transparency-not-supported-by-desktop-quot
It is annoying when people resurrect months old threads for no apparent reason, but starting a new thread on the same topic within a week is also a waste of time.
I had thought this would be a very odd problem happening only to me.