The include directories are set here: https://github.com/projectNe10/Ne10/blob/master/modules/CMakeLists.txt#L363C22-L363C22
That doesn't work with Ne10 used as submodule or via FetchContent, as PROJECT_SOURCE_DIR is the directory of the project USING Ne10, not Ne10 itself.
target_include_directories(NE10 PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/inc)
should be used in top-level CMakeLists.txt instead.
The include directories are set here: https://github.com/projectNe10/Ne10/blob/master/modules/CMakeLists.txt#L363C22-L363C22
That doesn't work with Ne10 used as submodule or via FetchContent, as PROJECT_SOURCE_DIR is the directory of the project USING Ne10, not Ne10 itself.
target_include_directories(NE10 PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/inc)should be used in top-level CMakeLists.txt instead.