Sync speaker volume when using multi-room audio with this one weird trick™ https://www.youtube.com/watch?v=WMNbxGvs61w
Sync Volume of AirPlay 2 Multi-room Audio Groups on iPhone

YouTube
@bzamayo oh god I have a quiet Sonos Roam and a pair of 2018 HomePods. If they’re the same volume the whole building hears it and I think I’ve accidentally discovered this gesture a few times (and thought it was a bug)
@Lapfelix haha, somewhat related I wish you could cap the max volume on the HomePod in the settings, as 100% is way too loud
@bzamayo YES does anyone at Apple live in an apartment?
@Lapfelix @bzamayo Nah they all live in a replica of this. Like in Severance.
@bzamayo I had no idea you could this. I achieved this by turning them all down to 0 then using the volume slider 🤯