You misread the problem, Ernie.
The question is... "getitng rid of audio delay on Yamaha receiver".
The fact the OP mentioned Sonos is a red-herring.
The source could be a CD player.
It could be a turntable.
That's not the point.

The issue is delay with multiple Yamaha pieces of kit, not with the Sonos. The Sonos is simply the source into a multi-zone receiver.

The OP notes: "If I have an Sonos connect being shared by the Yamaha and multi-room audio amp connected analogue, I can't get rid of the delay unless I set the amp top direct mode."

In other words, when the Sonos is the source, connected to the Yamaha via RCA = delay.
Connected via digital = delay.
The work arounds are 'direct' or 'party mode' but they make it tricky to automate.

I've noted that setting the MusicCast implementation is baked into the Yamaha AVR's, meaning that it will alter how the receiver handles multiple zones, whether using the MusicCast app - or not.

Choosing 'audio sync' in MusicCast makes the issue go away when the Sonos source is connected.