I do not know to what extent you may be willing to allow a Raspberry Pi based system to enter your audio chain, but I can suggest moOde audio.
Has for sure all you demand, except I am not sure about Neutron / and the likes. It can do, OTOH, Spotify connect and LMS / Squeezebox / BT / AirPlay...
Worth a look, IMHO, for as much as a 100 bucks... or whatever a Pi4 is worth ATM (just because the Pi5s are more expensive, power-demanding, and producing more heat, hence demanding cooling solutions that may be "noisy"...) I have a Pi4, and rocks. In any sense.
Outputs its UI to HDMI and via web. Outputs audio to USB, HATs, and HDMI. Any HAT providing more outputs will allow for S/PDIF / I2S and the like.
HTH
Cheers, Al.