We have a WIP version of cffi that builds on the free-threaded interpreter: Quansight-Labs/cffi-ft#1

I think with that it should now be possible to make some headway on free-threaded support without too much hacking to disable things.

Unfortunately we're still blocked on releasing cp313t wheels to users until CFFI support is merged, unless there's any appetite to depend on our fork. There isn't a way to depend on the fork only on the free-threaded build because environment markers don't know about ABI tags. We're hoping to have a PEP and a fix for that in Python 3.14 but that doesn't really help much right now or in the next few years.