It seems that the new style is preferred now.
After the connection conversion, gcc compiler warns about KIO::Job::canceled deprecation. API docs say that it can be safely replaced with result() "and error() is, in this case, ERR_USER_CANCELED." So we do.
https://api.kde.org/frameworks/kio/html/classKIO_1_1Job.html#a16f78937ceba1bf95ca9852ddbd5c5b5