Recommendations for Blu-ray Player

HiMedia S500 player with a linear power supply.  It's one of the only two "generic" Android 9.0 OS devices, supporting full AndroidTV and Google Play apps, including Amazon Music for HD.  Alternatively, Nvidia Shield, but it has a proprietary power cable.

Maybe FireTV Cube with linear power supply, but it has a smaller non-standard DC plug.  An SBooster with all the different adapters would likely work).

Roku with linear power supply?

Unfortunately, all these devices only output audio through HDMI.  There really isn't any device that does what you want and still has a digital COAX output.

Oppo 103/105 is an excellent platform for streaming, but options are limited.  I know it streams Netflix and only a few other providers. It does NOT stream anything from Amazon.

The problem with optical toslink is that the light emitting diodes (LED) cannot light up fast enough to produce a perfect square wave.  The wave comes out almost curvy (almost like an analog sine wave).  You also have potential problems with the light receiver.  As far as how this affects sound quality, I can't really say. But I have compared toslink to COAX and COAX is always better as long as you have a good digital cable.