We've published an initial experimental release for the Pixel 9 Pro Fold on our staging site:

https://staging.grapheneos.org/releases#comet-stable
https://staging.grapheneos.org/install/web

Our preordered Pixel 9 Pro Fold for our device testing farm hasn't arrived yet so we'll be relying on others to test the early builds.

Everything from #GrapheneOS been ported for it already and there's nothing else to do for it without testing feedback from users. There's a high chance everything is already fine for it since we have production quality support for the other 9th gen Pixels and the original 7th gen Pixel Fold.