I made a thing!
https://hugovk.github.io/free-threaded-wheels/ tracks how many of the top 360 PyPI packages have free-threaded wheels.
Green packages (currently 3%) offer has free-threaded wheels
Uncoloured packages (82%) offer pure-Python wheels
Orange packages (16%) have no wheels ready for free-threading (yet!)
See also Quansight Labs' https://py-free-threading.github.io/tracking/ for a smaller yet fine-grained tracker that also includes build tools.