Created attachment 105857 [details] Backtrace, which was not submitted by the crash reporter as useless. Software Center (plasma-discover) usually locks up within a minute, if searching for a package by a keyword. Also, searching is bad UX, the focus should be on the text entry field by default. There is no plasma-discover-dbg package for Kubuntu and the crash reporter cannot produce a usefull backtrace, working at 100% CPU for many hours. I had to kill the (locked-up) plasma-discover process, which was consuming 100% CPU during backtrace generation (and probably since the lockup, but not before lockup). Also, plasma-discover consumes 500MB resident memory after the lockup, compared to 100MB immediately after launch. This is easy to reproduce.
Created attachment 105859 [details] valgrind log, crash comes when exiting Discover Discover was run as root, with valgrind prefix. Middle part of the log file is absent (nothing new there). A few applications were successfully installed, crash comes when exiting Discover (this is typical).
Maybe related to problem is that my display DPI is set to 66 to reduce all font sizes. Discover alone is unique in rendering unreadable "greek" text before the first window change (update).
*** This bug has been marked as a duplicate of bug 378339 ***