While find_package is commented out (I guess because of some discovery issues) find_library approach would have the same functionality but also allow to put CMake flag -DActs_ROOT... to set ACTS directory if it is not in the standard place. Acts_ROOT - is the recommended name by CMP0074 cmake policy

CMakeLists.txt

@@ -2,10 +2,12 @@ cmake_minimum_required(VERSION 3.3 FATAL_ERROR)
 PROJECT(reference_detector
   VERSION 0.0.1
   LANGUAGES CXX
-  DESCRIPTION "A template dd4hep+acts detector"
+  DESCRIPTION "EIC Reference Detector (via dd4hep+acts)"
   )
 
 find_package( DD4hep REQUIRED COMPONENTS DDCore DDG4 )
+find_library(ACTS_CORE_LIBRARY NAMES ActsCore HINTS ${Acts_ROOT} $ENV{Acts_ROOT} PATH_SUFFIXES lib lib64)
+find_library(ACTS_PLUGIN_DD4HEP_LIBRARY NAMES ActsPluginDD4hep HINTS ${Acts_ROOT}  $ENV{Acts_ROOT} PATH_SUFFIXES lib lib64)
 
 #find_package(Acts REQUIRED COMPONENTS Core IdentificationPlugin TGeoPlugin DD4hepPlugin PATHS /home/whit/lib/cmake NO_DEFAULT_PATH)
 #find_package(Acts REQUIRED COMPONENTS Core PluginIdentification PluginTGeo PluginDD4hep )
@@ -16,7 +18,7 @@ set(a_lib_name reference_detector)
 dd4hep_configure_output()
 
 dd4hep_add_plugin(${a_lib_name} SOURCES src/*.cpp
-        USES ActsCore ActsPluginDD4hep
+        USES ${ACTS_CORE_LIBRARY} ${ACTS_PLUGIN_DD4HEP_LIBRARY}
   )
 target_link_libraries(${a_lib_name}
   PUBLIC DD4hep::DDCore  DD4hep::DDRec