Cmake find_package does not work with Doxygen - cmake

Question

Objective
I am trying to have CMake find Doxygen on a bunch of different systems and configurations:
Online documentation is generated on Ubuntu
Local tests and development is done on Macos
Doxygen can be installed system-wide, through brew or through conan depending on the use case
Problem
I struggle finding a uniform approach that does not involve a lot of OS-specific operations. I am vaguely tempted to glue together the 3 following approaches, but I am still surprised/concerned/unsure a more elegant solution does not exist.
Sub-solution 1
What I have presently works only for system-wide installations:
find_package(Doxygen
REQUIRED dot
OPTIONAL_COMPONENTS mscgen dia)
if(DOXYGEN_FOUND)
# doxygen settings can be set here, prefixed with "DOXYGEN_"
# ...
# this target will only be built if specifically asked to.
# run "make docs" to create the doxygen documentation
doxygen_add_docs(
docs
${PROJECT_SOURCE_DIR}
COMMENT "Generate API-documents."
)
else (DOXYGEN_FOUND)
message([WARNING] " Doxygen need to be installed to generate the doxygen documentation")
endif (DOXYGEN_FOUND)
Sub-solution 2:
I am aware I can try to access Conan-installed executable through CONAN_BIN_DIRS_DOXYGEN/doxygen, as explained here
Sub-solution 3:
I am also aware I can try to locate Homebrew installations as described here.

Answer 1

Following #drodri comments, the following conan/conanfile.py achieves the desired result for my header-only library:
from conans import ConanFile, CMake
from conan.tools.cmake import CMakeDeps
class MyConan(ConanFile):
name = "mylib"
version = "0.1"
settings = "os", "compiler", "arch", "build_type"
exports_sources = "include/*", "CMakeLists.txt", "test/*", "cmake/*", "docs/*"
no_copy_source = True
generators = "cmake", "CMakeToolchain", "CMakeDeps"
requires = "boost/[>=1.78.0]", "gdal/[>=3.4.3]"
tool_requires = "cmake/3.24.2", "doxygen/1.9.4"
def generate(self):
cmake = CMakeDeps(self)
# generate the config files for the tool require
cmake.build_context_activated = ["doxygen/1.9.4"]
cmake.generate()
def build(self): # this is not building a library, just tests
cmake = CMake(self)
cmake.configure()
cmake.build()
cmake.test(output_on_failure=True)
def package(self):
self.copy("*.h")
def package_id(self):
self.info.clear()
It can be called with conan install conan/conanfile.py --build=missing --install-folder=build -pr:b=conan/profiles/clang_13 -pr:h=conan/profiles/clang_13