That said, removing the bi-amp capability may technically break trueplay, but I don’t see how. If it worked in single channel mode as a sub, it should work bridged like this.
[edit] just looked at his gen1 guide that does the same mono-bridging, and it claims trueplay still works. Which makes sense - trueplay is a feedback loop. With the speaker playing specific frequencies at specific volumes, and your phone listens to it and adjusts the DSP to make those frequency/volume pairs match what it expects.
Not all amps are equal. The Sonos Amp can competently drive 4 beefy in-wall/ceiling speakers. The Sonos Amp isn't just the guts of this product marked up 5x.
Either way, it's silly that Sonos doesn't have a simple un-amplified receiver for similar setups. Perhaps they are afraid consumers would get confused about non-amplified products given all their other products are amplified.
They do have that, the Sonos Port, but it's extremely overpriced at $449. They very gracefully do allow you to get a full two channels of audio (stereo) though.
If you use them to bi-amp speakers with two drivers, the TruePlay calibration works great.
Or Chromecast audio to hifi.