For anyone currently having trouble setting up PCSS: Both VRCFury and NDMF (required for Modular Avatar) currently break PCSS when entering play mode/uploading. This is likely due to something with how they optimize the avatar, and seeing how both Fury and NDMF break PCSS, and trying older version combinations of all of them that I know worked previously, it's likely a Unity or VRCSDK update that actually borked it.
The PCSS dev has the issue with Fury in the known issues on his discord but no mention of MA/NDMF. I did make a post in the Discord today about NDMF so that may get added to the known issues. I'm not sure if he's actually trying to fix it since apparently Fury has been breaking PCSS since at least January, seeing how the known issues post was from 2/4/25. Not sure when NDMF became an issue, if at the same time or more recently. Fury/NDMF devs can't fix it on their end since this is definitely an issue with PCSS itself.