OST 1.8 is enough for cmake.

CMakeLists.txt

@@ -86,7 +86,7 @@ if(NOT DISABLE_DOCUMENTATION)
   # set this to the URL corresponding to the version of OST you are using
   set(OST_DOC_URL "https://www.openstructure.org/docs/dev")
 endif()
-find_package(OPENSTRUCTURE 1.9 REQUIRED 
+find_package(OPENSTRUCTURE 1.8 REQUIRED
              COMPONENTS io mol seq seq_alg mol_alg conop img mol_mm)
 
 if(CMAKE_COMPILER_IS_GNUCXX)