HI @ofwaih
Welcome to the Sonos Community!
In short, no - not with the Yamaha. The Sonos Playbar effectively works as a receiver itself - it cannot be used as a speaker for another receiver, and it will not work in conjunction with non-Sonos devices (apart from your TV).
What will work is a Sonos Amp - it can connect to your in-ceiling speakers (assuming they’re 4-8 Ohms) and wirelessly connect to the Playbar directly (though it must be in range to do so - ethernet connections on both are required otherwise) to operate as Surround speakers.
Although you can connect 4 speakers (if they’re 8 Ohms) to a Sonos Amp, they are not switchable, and all 4 will play. For your outdoor speakers, you could connect a second Amp, or connect your Yamaha and get a Sonos Port (cheaper than the Amp) to be the input to it so you can play Sonos sources outside (and synced with inside). This would also allow you to play sources connected to the Yamaha across your Sonos system (typically, you’d connect a Port to Tape In and Tape Out on the receiver, if available).
A cheaper option than an Amp would be to get a discontinued, second-hand Connect:Amp, though be sure to buy one that is S2 (our new control software version) compatible. If you get one of these, both it and the Playbar must be connected via ethernet.
I hope this helps, and if you have any further questions, please don’t hesitate.
"Common sense is the collection of prejudices acquired by age eighteen." - Albert Einstein