Is there an adapter that allows a Phase One back to be attached to a Hy6 camera?

Phase One backs have a mount built into the back. They do not use an adapter system.

Are there P1 backs that mount to the Sinar cameras?

Not to the Hy6/AFi.

This has been debated to death on this forum.
I suggest the topic be dropped now.

Edmund

To view cameras, like the Sinar p/p2, x and p3: YES

Thierry

Phase One makes a "Flex Adapter". I have been using it on a Sinar P2 with a P-45+.
It works well if you have the right lenses. It also allows stitching images together for larger files. You can get plates for any Mount of Phase one back. Kapture Group also makes sliding back adapters.
It is nice to be able to go back and forth between the view camera and medium format system as needed.
My only caveat, is the P2 movements don't work as precisely with the smaller digital chips as they seemed to, with 4x5 film

As someone else pointed out, the Phase backs don't work with the Hy6 and it has been talked about quite a bit.

Why are you so negative..... it's not over yet!!! Phase already has something
ready, we may be surprised!!!

Apologies, the words Sinar, Phase One, and Hy6 return too many search results.

Are the Leaf Aptus and Sinar eMotion backs communicative with the camera in a way that prohibits other back makers to join the system?

Could you please elaborate?

Unfortunately, not at this point!!!

If at some point I can put my P20 on a Hy6.... that would be something.