OK, Streamers: "Head" units only...?

How about Roon Nucleus connected directly to your Chord Qutest via USB. I know by your definition it may not qualify as strictly a "head unit", but it definitely meets all of your other criteria, including your budget and arguably the best app out there.

At list price
Roon Nucleus ...........$1399
Roon Lifetime ........... $699 (or alternatively $119 annually)
Curious USB Cable ... $350
=====================
Total outlay ............. $2448

One caveat: support for subscription streaming services currently limited to Tidal and Qobuz.

These are exactly the components I am doing today in my main rig and I’m loving it. And btw, my evolutionary track included Bluesound kit which I am now using elsewhere in my household as Roon endpoints. And yes SQ as well as app are both better than with Bluesound Node 2i in my system. And as it so happens the DAC in my main rig is also a Chord Qutest.

Right but as you said only Tidal and Qobuz. No amazon and probably not any time soon if ever.
Amazon Music may not be where it’s at forever but before it’s done it is going to wash over everything.
I believe I made that original post.
The thing is I think there are absolutely spectacular electronics available and it seems that their respective firmware is great (I can’t really say this with authority but these devices work, right, albeit within their limits) but currently available software is simply just not equally good for the task of a good streaming experience. Every one of these programs has either major limitations (to me) or major flaws, or both.
To answer your question about Bluesound and blueOS; I am incredulous at the support that company gets on here. The dac in a Bluesound node can be bettered by the dac in most any $35 Chi-Fi gizmo out there. Honestly, the only dac I’ve ever heard that’s worse than the one in the Bluesound Node is the one in the Chromecast Audio. And BlueOS!?!? Shamefully unfriendly, maddeningly buggy, and wont do about a hundred things that It should do. An absolutely horrible effort at software development and support that I believe that company should be ashamed of.

Following this thread closely. I’ve spent hours pouring over solutions to this problem. I have a stand alone Dac that I love and the synergy in my system is excellent. I know there are many in the same boat looking for a high end streamer that only streams. I don’t want any thing else. Sounds simple right? Its not.

(Things I don't need or want: Remote, Volume Attenuation, Dac, Ripper, Storage, Indexing, A crappy App, CD player, a bunch of jitter/noise, bluetooth....I think that's it.)

Upping a Bluesound would be moving to an Aurender.
Unfortunately, Aurender only offers Qobuz and Tidal, so if you want the variety Bluesound offers, your going to have to stay with them.
That being said, upgrade to a high quality DAC- like Ayre Codex or Schiit Gungnir or Yggy ( I mention these only because they outperform from their price points).
I have listened to both Aurender and Bluesound with the Codex and can say it is a very good match for the money.
Bob