Quest AR Passthough Shadows

I’m currently looking into the best way to implement shadows for virtual characters. I’ve seen a few ways that look promising with just drop shadow cards. But what if I want true dynamic shadows? How do I get them to cast with no floor mesh since I want Passthrough? Or even dynamic soft shadows? I came across this for dynamic soft shadows based off the collision which looks pretty good. But how would I implement that with Passthrough?

Here is a sneak peak at the current project. The characters still don’t feel grounded yet without shadows. Just trying to find the best and most realistic way.

Please share your thoughts an how you think the best way to implement a shadow for so many characters should work in Passthrough!