KAUTH_INSTALL_HELPER_FILES code uses the deprecated DBUS_SYSTEM_SERVICES_INSTALL_DIR variable, which will not be set when KDE_INSTALL_DIRS_NO_DEPRECATED is set, so the code will fail.
KDE_INSTALL_DBUSSERVICEDIR replaces it?
https://api.kde.org/ecm/kde-module/KDEInstallDirs.html says that it is KDE_INSTALL_DBUSSYSTEMSERVICEDIR
A possibly relevant merge request was started @ https://invent.kde.org/frameworks/kauth/-/merge_requests/5
Git commit 0068b2176afeb8661b8b26950c9bee79c8fb86ec by Harald Sitter. Committed on 16/09/2020 at 12:56. Pushed by sitter into branch 'master'. use new install var DBUS_SYSTEM_SERVICES_INSTALL_DIR is deprecated, KDE_INSTALL_DBUSSYSTEMSERVICEDIR is not. use the latter. we depend on latest ECM anyway, what with it being a framework, so we can use the not deprecated version easy peasy FIXED-IN: 5.75 M +1 -1 cmake/KF5AuthMacros.cmake https://invent.kde.org/frameworks/kauth/commit/0068b2176afeb8661b8b26950c9bee79c8fb86ec