I've found this. I haven't tried it, but I want to save it just in case.
Contents:
Boost has experimental CMake support. You have to do a bit of dev to get it working but we've had good experiences so far.
set(BOOST_INCLUDE_LIBRARIES system thread) # enabled libraries
set(BOOST_ENABLE_CMAKE ON) # CMake support
FetchContent_Declare(boost GIT_REPOSITORY https://github.com/boostorg/boost.git ...
The above will get you the compiled libs working. For the header library (Boost::boost aka Boost::headers) there doesn't seem to be CMake support as yet so we wrote a few lines of CMake code to iterate through the FetchContent source directory and added all include folders to a new IMPORTED INTERFACE target.