Thanks for the info!
So continuous TRIM (discard) may be bad for some older SSDs, but OK for other (newer) SSDs.
But periodic TRIM is good for all, so I’ll probably start using that, since it shouldn’t have much downsides.
I don’t know if KDE has something else by default that enables usage of kdevelop, will test it as soon as possible.
Just found out that Xfce does not, and installing those packages makes kdevelop work.