Error building gui in Linux (Debian based)

[rbnpi]

Tried both Raspberry Pi (bookworm based) and debian Tricksy (latest)
Both produce this in the log

-- CMakeLists: Tau5
-- Building Tau5 version:  (commit: 74278a8)
-- DEVELOPMENT BUILD - Server at source tree: ../../../server
-- Could NOT find Cups (missing: CUPS_LIBRARIES CUPS_INCLUDE_DIR) 
-- App Root: 
-- 
-- ==============================================
-- Tau5 Build Configuration Summary
-- ==============================================
-- Build Type: DEVELOPMENT
-- Server Path: ../../../server
-- Binaries will look for server in source tree
-- Optimization: Release
-- Platform: Linux
-- ==============================================
-- Configuring done (0.1s)
CMake Error in external/qwindowkit-1.4.0/src/core/CMakeLists.txt:
  Imported target "Qt6::CorePrivate" includes non-existent path

    "/usr/include/aarch64-linux-gnu/qt6/QtCore/6.8.2"

  in its INTERFACE_INCLUDE_DIRECTORIES.  Possible reasons include:

  * The path was deleted, renamed, or moved to another location.

  * An install or uninstall procedure did not complete successfully.

  * The installation package was faulty and references files it does not
  provide.

the path is actually "/usr/include/aarch64-linux-gnu/qt6/QtCore/" without the Qt version number. (on Pi give 6.4.2 for version number)

Any idea where I can alter this? It used to build OK before you added the qwindowkit-1.4.0

Mac build works perfectly