Can I buy a streamer that has a digital audio output other than HDMI? (Because if the audio signal passes through my television it's been reduced to crap.) I can deal with USB, Coax, or Optical - anything other than HDMI. To utilize ROKU (the least expensive device in the chain), or most other streamers, it seems I have to upgrade my television (to get an un-defiled pass-through of the digital audio signal), or DAC (to accept audio via HDMI). WHY?
Are you asking about a video streamer.
I can't think of a current video streamer that has a digital audio output. Why?
The only way to pass Dolby TrueHD or Atmos is over HDMI. If you have the means to play them you have an HDMI input you can use and don't need to go through the TV that won't pass these signals. The next generation of HDMI-ARC will do so.
Not sure why you think your TV is degrading standard Dolby Digital which most will pass but it you have to use an HDMI audio extractor to provide a SPDIF digital audio output from any streamer.
If you are streaming audio only then a digital audio output is available on the Sonos Connect, Denon Heos, and most other streamers.