Just thought I'd post this up here as I've troubleshooted my configuration and I think I finally figured out what my issue was.
I have an eero wifi mesh system (3 eeros for what it's worth), and Sonos boost, Sonos connect:amp and some play:5's, as well as an ethernet switch next to my router.
My problem had been that on wifi (the eero) initially, I had been able to connect but my iOS controllers would lose their connection to the Sonos network (while wifi in general was still fine).
The first thing I did was to set my modem to passthrough mode, and let the eero do all the router work. At this point my system had a configuration of:
I was still experiencing connection issues, and purchased a Boost. I could not get the Boost to be recognized at all by the eero network when the Boost was connected to the switch at all.
Finally (duh) figured out to put one of my eeros as:
And connecting the Boost to the switch recognized instantly (and fingers crossed, no drop outs yet for scenarios that were easy to reproduce previously).
Anyways, hope this helps somebody (I should have figured this out initially I guess! I thought that the eeros system off the switch would have handled everything ok; but the Boost just needed to be behind the eero all the time)