Well a workaround is mounting and using joins ?

Now, be careful the example find duplicate file names (with equal size). Not duplicate files ! Those would require check of the contents of the file.

Also there are tools like fdupe, same problem regarding remote hosts though. Some tools use xattr to store hashes. Some might use DB's. (With xattr tools, you just run the tool on the remote host first, then on the local host, if you need to save bandwith.)

I however don't have the perfect answer.