@aeneas I own a Sony STR-DN840 and the S/PDIF is also only working till 96kHz rates.
Perhaps, this could be interesting for you but costs some bucks: HDMI audio passthrough LG B6P? - #6 by JimKnopf
The idea is to split the HDMI with the HDFury AVR Key to a signal for your TV and your AVR.