Maybe you can use optical to usb converter like this https://hifimediy.com/product/hifime-ur23-spdif-optical-to-usb-converter/ . However I think you may need to get a female usb A type to usb-c male adapter. Specs say signal supported up to 96khz/24 bit
Topping d50 III has different dimension from d50s as shown from topping site https://www.toppingaudio.com/product-item/d50-iii . Looks like it is taller than d50s
Whatever... the early customers are usually lab rats for new and untried products but companies need to wade in the waters of uncertainty otherwise the status quo remains and the audiophile market desperately need change.
After giving my son the kz zs10pro, I bought another pair and use it with my Sony WM1A dap. I'm using the kz coz of its low impedance and the wm1a has low power. The wm1a drives the kz well. I must say I'm really enjoying this pairing.
If you are seriously contemplating on doing that, the sk02 hp out can easily be connected to an adapter like below and its female out can jut out from the hole in your desk