There’s a ’Chinese Black-Box’ available from a couple of eBay sellers that takes an HDMI input from a SACD player (like an OPPO) and strips the video signal, passing the DSD audio layer to a variety of output types, including i2s. I bought one but I haven’t used it yet. It took weeks to get here from China even though I paid for expedited shipping and came sans wall-wart and any instructions. (Though a standard wall-wart will work and operation is pretty self-explanatory since it’s just a simple pass-through device.)
PS - The HDMI output from a SACD player is not i2s compatible in any way. SACD players use the 'true' HDMI format which carries the audio and the video signal. I2S is not HDMI, it just happens to use the same plug type, in some instances. So for example, my Denafrips supports i2s, but it won't recognize or decode a signal coming from the HDMI output on my OPPO SACD player, it needs to be converted (in my case, via the Chinese BB). I know most of you know this, but there are some who possibly do not.