It appears that ksudoku isn't properly included in the kdegames package. It's mentioned in Makefile.common but isn't installed as part of the package.
A commit references this bug: Author: tcberner Date: Fri Jul 10 18:13:18 UTC 2020 New revision: 541876 URL: https://svnweb.freebsd.org/changeset/ports/541876 Log: games/kdegames: add option of games/ksudoku PR: 247897 Reported by: anahata <cnehren@pobox.com> Changes: head/games/kdegames/Makefile head/games/kdegames/Makefile.common
It's added now. Thanks for the report. mfg Tobias