If you want to use phone as source, you can use USB DACs like AKHC4, Cayin RU6 etc and connect using analog interconnects to DSP. This plenty of usb dac options available in market.
If you want to connect using optical or coiax, sources with digital out is quite less in the market.
Another way is to use an android headunit and connect it to usb dac, if the usb dac has an optical out you can leverage that or use the analog out to DSP.
I used the first option which I mentioned in Vento